ASTM D7155-20
(Practice)Standard Practice for Evaluating Compatibility of Mixtures of Turbine Lubricating Oils
Standard Practice for Evaluating Compatibility of Mixtures of Turbine Lubricating Oils
SIGNIFICANCE AND USE
5.1 The compatibility of oils can be important for users of oil-lubricated equipment. Mixing of two oils can produce a substance markedly inferior to either of its constituent materials. One or more of the following can occur:
5.1.1 A mixture of incompatible oils most often forms a precipitate. The precipitate will form unwanted deposits in the lubrication system, plug filters, and oil passageways.
5.1.2 A mixture of incompatible oils will sometimes exhibit degradation of certain performance parameters like demulsibility, foam inhibition oxidation stability, rust protection ability, or antiwear protection ability.
5.1.3 A mixture of incompatible oils will sometimes exhibit non-miscibility of the base oils with each other.
5.1.4 Such incompatibilities can lead to catastrophic equipment failures.
5.2 To minimize the chances of these problems occurring, lubricant suppliers recommend evaluating compatibility of lubricating oil of different formulations and sources prior to mixing. Equipment users most often do not have the resources to evaluate oil compatibility and must rely on their suppliers. Mixing of oils without first determining the compatibility is a highly imprudent practice.
5.3 Although new turbine oils may be compatible, in-service oil of the same type may be degraded or contaminated to such an extent that the new oil added may not be compatible with the system oil. In-service oil compatibility with new oil additions should be evaluated on a case-by-case basis.
5.4 The oxidation resistance of different oils of the same type can vary widely, and compatibility does not imply equivalent performance without oxidation performance testing.
SCOPE
1.1 This practice covers the compatibility of mixtures of turbine lubricating oils as defined by Specification D4304. The methods compare properties of specific mixtures with those of the neat oils after storage at specified conditions.
1.2 The methods are grouped into four tiers of testing types:
1.2.1 Tier 1—Visual appearance
1.2.2 Tier 2—Interfacial properties
1.2.3 Tier 3—Physical and chemical properties
1.2.4 Tier 4—Specific performance properties
1.3 The methods can be used to evaluate new (unused) lubricant compatibility or the effects of adding new (unused) lubricant to in-service lubricant in the system.
1.4 This practice does not evaluate the wear prevention characteristics, load carrying capacity, or the mechanical shear stability of lubricants mixtures while in service. If anti-wear (AW), extreme pressure (EP), or shear stability are to be evaluated, further testing of these parameters may be required.
1.5 Mixtures of the two constituent oils are evaluated using the Tier 1 and Tier 2 testing protocol. Sequential or concurrent testing is continued by applying tests from Tier 3 or Tier 4 until the test requestor or user is satisfied that the intent of this practice has been met. If any mixture fails the methods, the oils are considered incompatible by that method. If all mixtures pass the methods, the oils are considered compatible by those methods. It is recommended that passing only Tier 1 does not adequately test for fluid compatibility.
1.6 If the mixture passes Tier 1, it shows two oils are visually compatible only. If the mixture passes Tier 1 and 2, it shows two oils are visually and interfacially compatible. If the mixture passes Tier 1, 2 and 3, it shows two oils are visually, interfacially, physically, and chemically compatible. If the mixture passes Tier 1, 2, 3, 4, it shows two oils are compatible with the highest confidence level. Testing each tier level is giving the user more confidence that the two fluids are compatible.
1.7 This practice applies only to lubricating oils having characteristics suitable for evaluation by the suggested test methods. If the scope of a specific test method limits testing to those oils within a specified range of properties, oils outside that ...
General Information
- Status
- Published
- Publication Date
- 30-Apr-2020
- Technical Committee
- D02 - Petroleum Products, Liquid Fuels, and Lubricants
- Drafting Committee
- D02.C0.01 - Turbine Oil Monitoring, Problems and Systems
Relations
- Effective Date
- 01-May-2020
- Effective Date
- 01-Apr-2024
- Effective Date
- 01-Mar-2024
- Refers
ASTM D4175-23a - Standard Terminology Relating to Petroleum Products, Liquid Fuels, and Lubricants - Effective Date
- 15-Dec-2023
- Effective Date
- 01-Dec-2023
- Effective Date
- 01-Nov-2023
- Effective Date
- 01-Oct-2023
- Refers
ASTM D4175-23e1 - Standard Terminology Relating to Petroleum Products, Liquid Fuels, and Lubricants - Effective Date
- 01-Jul-2023
- Effective Date
- 01-Jan-2020
- Effective Date
- 01-Dec-2019
- Effective Date
- 01-Jul-2019
- Effective Date
- 01-May-2019
- Effective Date
- 01-May-2019
- Effective Date
- 01-Oct-2018
- Effective Date
- 01-Apr-2018
Overview
ASTM D7155-20 - Standard Practice for Evaluating Compatibility of Mixtures of Turbine Lubricating Oils provides a comprehensive framework for assessing the compatibility of turbine lubricating oils before mixing. Compatibility evaluation is critical because mixing incompatible turbine oils can result in degraded performance, formation of precipitates, filter blockages, or catastrophic equipment failures. This standard outlines a systematic multi-tiered approach for compatibility testing, helping prevent operational issues and extending the life of lubrication systems.
Key Topics
Significance of Lubricant Compatibility
Mixing turbine lubricating oils from different sources, formulations, or even oils of the same type (but at different degrees of service or oxidation) can cause unexpected reactions. Potential outcomes of incompatibility include:- Formation of precipitates or deposits
- Decreased demulsibility and foam inhibition
- Reduced oxidation and rust protection
- Non-miscibility of base oils
- Overall performance degradation or system failure
Tiered Testing Approach
ASTM D7155-20 defines four key tiers of compatibility testing:- Tier 1: Visual Appearance
Initial inspection for clarity, sediment, or cloudiness. - Tier 2: Interfacial Properties
Testing for properties such as water separability, foaming, and air release, which indicate how the oils interact at their boundaries. - Tier 3: Physical and Chemical Properties
Assessment of viscosity, acidity, additive elements, and other fundamental oil properties to detect unexpected shifts due to blending. - Tier 4: Performance Properties
Where needed, additional evaluation of properties such as oxidation stability and rust/corrosion resistance to establish highest confidence in mixture suitability.
- Tier 1: Visual Appearance
Interpretation of Results
- Oils must pass all required tests at each tier to be deemed compatible.
- Passing only Tier 1 is insufficient; higher-tier testing increases user confidence.
- In-service oils may require special consideration, as degradation or contamination can affect compatibility with new oils.
Applications
The procedures in ASTM D7155-20 are essential in industries where turbine reliability is paramount, including power generation, petrochemical processing, and heavy manufacturing. Practical uses include:
Oil changeovers and top-ups:
- Evaluate whether new batches or brands of turbine oil can be safely added to existing system oils.
- Prevent unintentional mixing that could lead to operational failures.
System conversions:
- Support plant engineers and maintenance teams when transitioning lubrication systems or switching oil suppliers.
- Ensure that legacy oils and replacement lubricants are compatible.
Supplier recommendations:
- Assist oil suppliers and laboratory technicians in providing reliable compatibility assessments for their clients.
- Support procurement decisions and maintenance planning.
Related Standards
ASTM D7155-20 references a range of supporting standards for test methods and definitions relevant to turbine lubricating oil compatibility, including:
- ASTM D4304: Specification for Mineral and Synthetic Lubricating Oil Used in Steam or Gas Turbines
- ASTM D1401: Water Separability of Petroleum Oils and Synthetic Fluids
- ASTM D445 & D7042: Kinematic and Dynamic Viscosity Methods
- ASTM D892: Foaming Characteristics of Lubricating Oils
- ASTM D665: Rust-Preventing Characteristics
- ASTM D2272: Oxidation Stability of Steam Turbine Oils
For a complete list, refer to the standard's referenced documents section.
Keywords: turbine oil compatibility, lubricating oil mixtures, compatibility testing, ASTM D7155, turbine lubricant performance, oil mixing, power plant lubrication, in-service oil evaluation, oxidation stability, lubricant performance testing.
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Frequently Asked Questions
ASTM D7155-20 is a standard published by ASTM International. Its full title is "Standard Practice for Evaluating Compatibility of Mixtures of Turbine Lubricating Oils". This standard covers: SIGNIFICANCE AND USE 5.1 The compatibility of oils can be important for users of oil-lubricated equipment. Mixing of two oils can produce a substance markedly inferior to either of its constituent materials. One or more of the following can occur: 5.1.1 A mixture of incompatible oils most often forms a precipitate. The precipitate will form unwanted deposits in the lubrication system, plug filters, and oil passageways. 5.1.2 A mixture of incompatible oils will sometimes exhibit degradation of certain performance parameters like demulsibility, foam inhibition oxidation stability, rust protection ability, or antiwear protection ability. 5.1.3 A mixture of incompatible oils will sometimes exhibit non-miscibility of the base oils with each other. 5.1.4 Such incompatibilities can lead to catastrophic equipment failures. 5.2 To minimize the chances of these problems occurring, lubricant suppliers recommend evaluating compatibility of lubricating oil of different formulations and sources prior to mixing. Equipment users most often do not have the resources to evaluate oil compatibility and must rely on their suppliers. Mixing of oils without first determining the compatibility is a highly imprudent practice. 5.3 Although new turbine oils may be compatible, in-service oil of the same type may be degraded or contaminated to such an extent that the new oil added may not be compatible with the system oil. In-service oil compatibility with new oil additions should be evaluated on a case-by-case basis. 5.4 The oxidation resistance of different oils of the same type can vary widely, and compatibility does not imply equivalent performance without oxidation performance testing. SCOPE 1.1 This practice covers the compatibility of mixtures of turbine lubricating oils as defined by Specification D4304. The methods compare properties of specific mixtures with those of the neat oils after storage at specified conditions. 1.2 The methods are grouped into four tiers of testing types: 1.2.1 Tier 1—Visual appearance 1.2.2 Tier 2—Interfacial properties 1.2.3 Tier 3—Physical and chemical properties 1.2.4 Tier 4—Specific performance properties 1.3 The methods can be used to evaluate new (unused) lubricant compatibility or the effects of adding new (unused) lubricant to in-service lubricant in the system. 1.4 This practice does not evaluate the wear prevention characteristics, load carrying capacity, or the mechanical shear stability of lubricants mixtures while in service. If anti-wear (AW), extreme pressure (EP), or shear stability are to be evaluated, further testing of these parameters may be required. 1.5 Mixtures of the two constituent oils are evaluated using the Tier 1 and Tier 2 testing protocol. Sequential or concurrent testing is continued by applying tests from Tier 3 or Tier 4 until the test requestor or user is satisfied that the intent of this practice has been met. If any mixture fails the methods, the oils are considered incompatible by that method. If all mixtures pass the methods, the oils are considered compatible by those methods. It is recommended that passing only Tier 1 does not adequately test for fluid compatibility. 1.6 If the mixture passes Tier 1, it shows two oils are visually compatible only. If the mixture passes Tier 1 and 2, it shows two oils are visually and interfacially compatible. If the mixture passes Tier 1, 2 and 3, it shows two oils are visually, interfacially, physically, and chemically compatible. If the mixture passes Tier 1, 2, 3, 4, it shows two oils are compatible with the highest confidence level. Testing each tier level is giving the user more confidence that the two fluids are compatible. 1.7 This practice applies only to lubricating oils having characteristics suitable for evaluation by the suggested test methods. If the scope of a specific test method limits testing to those oils within a specified range of properties, oils outside that ...
SIGNIFICANCE AND USE 5.1 The compatibility of oils can be important for users of oil-lubricated equipment. Mixing of two oils can produce a substance markedly inferior to either of its constituent materials. One or more of the following can occur: 5.1.1 A mixture of incompatible oils most often forms a precipitate. The precipitate will form unwanted deposits in the lubrication system, plug filters, and oil passageways. 5.1.2 A mixture of incompatible oils will sometimes exhibit degradation of certain performance parameters like demulsibility, foam inhibition oxidation stability, rust protection ability, or antiwear protection ability. 5.1.3 A mixture of incompatible oils will sometimes exhibit non-miscibility of the base oils with each other. 5.1.4 Such incompatibilities can lead to catastrophic equipment failures. 5.2 To minimize the chances of these problems occurring, lubricant suppliers recommend evaluating compatibility of lubricating oil of different formulations and sources prior to mixing. Equipment users most often do not have the resources to evaluate oil compatibility and must rely on their suppliers. Mixing of oils without first determining the compatibility is a highly imprudent practice. 5.3 Although new turbine oils may be compatible, in-service oil of the same type may be degraded or contaminated to such an extent that the new oil added may not be compatible with the system oil. In-service oil compatibility with new oil additions should be evaluated on a case-by-case basis. 5.4 The oxidation resistance of different oils of the same type can vary widely, and compatibility does not imply equivalent performance without oxidation performance testing. SCOPE 1.1 This practice covers the compatibility of mixtures of turbine lubricating oils as defined by Specification D4304. The methods compare properties of specific mixtures with those of the neat oils after storage at specified conditions. 1.2 The methods are grouped into four tiers of testing types: 1.2.1 Tier 1—Visual appearance 1.2.2 Tier 2—Interfacial properties 1.2.3 Tier 3—Physical and chemical properties 1.2.4 Tier 4—Specific performance properties 1.3 The methods can be used to evaluate new (unused) lubricant compatibility or the effects of adding new (unused) lubricant to in-service lubricant in the system. 1.4 This practice does not evaluate the wear prevention characteristics, load carrying capacity, or the mechanical shear stability of lubricants mixtures while in service. If anti-wear (AW), extreme pressure (EP), or shear stability are to be evaluated, further testing of these parameters may be required. 1.5 Mixtures of the two constituent oils are evaluated using the Tier 1 and Tier 2 testing protocol. Sequential or concurrent testing is continued by applying tests from Tier 3 or Tier 4 until the test requestor or user is satisfied that the intent of this practice has been met. If any mixture fails the methods, the oils are considered incompatible by that method. If all mixtures pass the methods, the oils are considered compatible by those methods. It is recommended that passing only Tier 1 does not adequately test for fluid compatibility. 1.6 If the mixture passes Tier 1, it shows two oils are visually compatible only. If the mixture passes Tier 1 and 2, it shows two oils are visually and interfacially compatible. If the mixture passes Tier 1, 2 and 3, it shows two oils are visually, interfacially, physically, and chemically compatible. If the mixture passes Tier 1, 2, 3, 4, it shows two oils are compatible with the highest confidence level. Testing each tier level is giving the user more confidence that the two fluids are compatible. 1.7 This practice applies only to lubricating oils having characteristics suitable for evaluation by the suggested test methods. If the scope of a specific test method limits testing to those oils within a specified range of properties, oils outside that ...
ASTM D7155-20 is classified under the following ICS (International Classification for Standards) categories: 75.100 - Lubricants, industrial oils and related products. The ICS classification helps identify the subject area and facilitates finding related standards.
ASTM D7155-20 has the following relationships with other standards: It is inter standard links to ASTM D7155-18, ASTM D445-24, ASTM D1500-24, ASTM D4175-23a, ASTM D665-23, ASTM D445-23, ASTM D892-23, ASTM D4175-23e1, ASTM D4310-20, ASTM D665-19, ASTM D6186-19, ASTM D6514-03(2019), ASTM D6514-03(2019)e1, ASTM D893-14(2018), ASTM D5762-18. Understanding these relationships helps ensure you are using the most current and applicable version of the standard.
ASTM D7155-20 is available in PDF format for immediate download after purchase. The document can be added to your cart and obtained through the secure checkout process. Digital delivery ensures instant access to the complete standard document.
Standards Content (Sample)
This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the
Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
Designation: D7155 − 20
Standard Practice for
Evaluating Compatibility of Mixtures of Turbine Lubricating
Oils
This standard is issued under the fixed designation D7155; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope* with the highest confidence level. Testing each tier level is
giving the user more confidence that the two fluids are
1.1 This practice covers the compatibility of mixtures of
compatible.
turbine lubricating oils as defined by Specification D4304. The
1.7 This practice applies only to lubricating oils having
methods compare properties of specific mixtures with those of
characteristics suitable for evaluation by the suggested test
the neat oils after storage at specified conditions.
methods. If the scope of a specific test method limits testing to
1.2 The methods are grouped into four tiers of testing types:
those oils within a specified range of properties, oils outside
1.2.1 Tier 1—Visual appearance
that range cannot be tested for compatibility by that test
1.2.2 Tier 2—Interfacial properties
method.
1.2.3 Tier 3—Physical and chemical properties
1.8 This practice may be used to evaluate the compatibility
1.2.4 Tier 4—Specific performance properties
of different types and grades of oil. However, it is not intended
1.3 The methods can be used to evaluate new (unused)
to evaluate such mixtures for lubrication performance. The
lubricant compatibility or the effects of adding new (unused)
user is advised to consult with suppliers in these situations.
lubricant to in-service lubricant in the system.
1.9 This practice does not purport to cover all test methods
1.4 This practice does not evaluate the wear prevention
that could be employed.
characteristics, load carrying capacity, or the mechanical shear
1.10 The values stated in SI units are to be regarded as
stability of lubricants mixtures while in service. If anti-wear
standard. The values given in parentheses after SI units are
(AW), extreme pressure (EP), or shear stability are to be
provided for information only and are not considered standard.
evaluated, further testing of these parameters may be required.
1.11 This standard does not purport to address all of the
1.5 Mixtures of the two constituent oils are evaluated using
safety concerns, if any, associated with its use. It is the
the Tier 1 and Tier 2 testing protocol. Sequential or concurrent
responsibility of the user of this standard to establish appro-
testingiscontinuedbyapplyingtestsfromTier3orTier4until
priate safety, health, and environmental practices and deter-
the test requestor or user is satisfied that the intent of this
mine the applicability of regulatory limitations prior to use.
practicehasbeenmet.Ifanymixturefailsthemethods,theoils
1.12 This international standard was developed in accor-
are considered incompatible by that method. If all mixtures
dance with internationally recognized principles on standard-
pass the methods, the oils are considered compatible by those
ization established in the Decision on Principles for the
methods. It is recommended that passing only Tier 1 does not
Development of International Standards, Guides and Recom-
adequately test for fluid compatibility.
mendations issued by the World Trade Organization Technical
1.6 If the mixture passes Tier 1, it shows two oils are Barriers to Trade (TBT) Committee.
visually compatible only. If the mixture passes Tier 1 and 2, it
2. Referenced Documents
shows two oils are visually and interfacially compatible. If the
mixture passes Tier 1, 2 and 3, it shows two oils are visually, 2.1 ASTM Standards:
D130 Test Method for Corrosiveness to Copper from Petro-
interfacially, physically, and chemically compatible. If the
leum Products by Copper Strip Test
mixture passes Tier 1, 2, 3, 4, it shows two oils are compatible
D445 Test Method for Kinematic Viscosity of Transparent
and Opaque Liquids (and Calculation of Dynamic Viscos-
ity)
This practice is under the jurisdiction ofASTM Committee D02 on Petroleum
Products, Liquid Fuels, and Lubricants and is the direct responsibility of Subcom-
mittee D02.C0.01 on Turbine Oil Monitoring, Problems and Systems. For referenced ASTM standards, visit the ASTM website, www.astm.org, or
Current edition approved May 1, 2020. Published June 2020. Originally contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
approved in 2006. Last previous edition approved in 2018 as D7155 – 18. DOI: Standards volume information, refer to the standard’s Document Summary page on
10.1520/D7155-20. the ASTM website.
*A Summary of Changes section appears at the end of this standard
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D7155 − 20
D611 Test Methods for Aniline Point and Mixed Aniline D7873 TestMethodforDeterminationofOxidationStability
Point of Petroleum Products and Hydrocarbon Solvents and Insolubles Formation of Inhibited Turbine Oils at
120 °C Without the Inclusion of Water (Dry TOST
D664 Test Method for Acid Number of Petroleum Products
Method)
by Potentiometric Titration
D8148 Test Method for Spectroscopic Determination of
D665 Test Method for Rust-Preventing Characteristics of
Haze in Fuels
Inhibited Mineral Oil in the Presence of Water
D892 Test Method for Foaming Characteristics of Lubricat-
3. Terminology
ing Oils
D893 Test Method for Insolubles in Used Lubricating Oils
3.1 For definitions of terms used in this test method, refer to
D974 Test Method for Acid and Base Number by Color-
Terminology D4175.
Indicator Titration
3.2 Definitions of Terms Specific to This Standard:
D1401 TestMethodforWaterSeparabilityofPetroleumOils
3.2.1 compatibility, n—of lubricating oils, the ability of
and Synthetic Fluids
lubricating oils to mix together without significant degradation
D1500 Test Method forASTM Color of Petroleum Products
of properties or performance.
(ASTM Color Scale)
3.2.1.1 Discussion—When a mixture of two oils has prop-
D2270 Practice for Calculating Viscosity Index from Kine-
erties or performance significantly inferior to either of the
matic Viscosity at 40 °C and 100 °C
constituent oils, then the two oils are incompatible. If the
D2272 Test Method for Oxidation Stability of Steam Tur-
properties are inferior to those of one neat oil but not inferior
bine Oils by Rotating Pressure Vessel
to those of the other, then such is not necessarily considered an
D3120 Test Method for Trace Quantities of Sulfur in Light
indication of incompatibility. To be considered significantly
Liquid Petroleum Hydrocarbons by Oxidative Microcou-
inferior, the property of the mixture would be worse than the
lometry
poorer of the two neat oils by an amount exceeding the
D3427 Test Method forAir Release Properties of Hydrocar-
repeatability (or in the case of third party verification testing,
bon Based Oils
the reproducibility) of the test method used to evaluate the
D4175 Terminology Relating to Petroleum Products, Liquid
property. (See the definitions for fail and pass.)
Fuels, and Lubricants
3.2.2 fail, n—in compatibility testing of oil mixtures, a test
D4304 Specification for Mineral and Synthetic Lubricating
result that is inferior to that of the poorer of the two constituent
Oil Used in Steam or Gas Turbines
oils by an amount exceeding the repeatability of the test
D4310 Test Method for Determination of Sludging and
method used for the evaluation.
Corrosion Tendencies of Inhibited Mineral Oils
3.2.3 insolubles, n—solids or semi-solid material that accu-
D4629 Test Method for Trace Nitrogen in Liquid Hydrocar-
mulate on the bottom of a liquid. As broadened, insolubles
bons by Syringe/Inlet Oxidative Combustion and Chemi-
includevarnishesand“non-sedimentatiousmaterials”resulting
luminescence Detection
from fluid incompatibility that change the appearance of a
D5185 Test Method for Multielement Determination of
bright and clear liquid to “hazy” or “cloudy.”
Used and Unused Lubricating Oils and Base Oils by
3.2.4 pass, n—in compatibility testing of oil mixtures, a test
Inductively Coupled Plasma Atomic Emission Spectrom-
resultthatisequaltoorbetterthanthatofthepoorerofthetwo
etry (ICP-AES)
constituentoilsbyanamountexceedingtherepeatabilityofthe
D5762 Test Method for Nitrogen in Liquid Hydrocarbons,
test method used for the evaluation.
Petroleum and Petroleum Products by Boat-Inlet Chemi-
luminescence 3.2.5 type and grade, n—type and grade refer to lubricants
D5846 Test Method for Universal Oxidation Test for Hy- of the same general type such as Rust and Oxidation Inhibited
turbine oil (R&O) and ISO Viscosity grades.
draulic and Turbine Oils Using the Universal Oxidation
Test Apparatus
3.2.6 10:90 mixture, n—a uniform blend of 10 % by volume
D6186 Test Method for Oxidation Induction Time of Lubri-
of one oil with 90 % by volume of a second oil.
cating Oils by Pressure Differential Scanning Calorimetry
3.2.7 50:50 mixture, n—a uniform blend of 50 % by volume
(PDSC)
of each of two component oils.
D6304 Test Method for Determination of Water in Petro-
3.2.8 90:10 mixture, n—a uniform blend of 90 % by volume
leum Products, Lubricating Oils, and Additives by Cou-
of one oil with 10 % by volume of a second oil.
lometric Karl Fischer Titration
D6514 Test Method for High Temperature Universal Oxida-
4. Summary of Practice
tion Test for Turbine Oils
D7042 Test Method for Dynamic Viscosity and Density of
4.1 Option 1—Prepare a 50:50 mixture of two oils to be
Liquids by Stabinger Viscometer (and the Calculation of
evaluated for compatibility. This mixture and the two neat,
Kinematic Viscosity)
constituent oils are tested using the compatibility tests. De-
D7843 Test Method for Measurement of Lubricant Gener- pending on the performance of the mixture, relative to those of
ated Insoluble Color Bodies in In-Service Turbine Oils
the constituent oils, 10:90 and 90:10 mixtures may need to be
using Membrane Patch Colorimetry tested in addition.
D7155 − 20
4.2 Option 2—Instead of testing mixtures in sequential Using Option 1, a 50:50 mixture and the two constituent oils
order, 10:90 and 90:10 mixtures are tested at the same time the are tested. If this mixture is found compatible, 10:90 and 90:10
50:50 mixture is evaluated. If all mixtures pass Tier 1 and 2 mixtures which reflect drain-and fill conversion or make up
compatibility tests, or if the application requires the evaluation proportionsmaybetested.UsingOption2,allmixtures(10:90,
of specific properties, Tier 3 and 4 compatibility tests can be 50:50, and 90:10) and the two constituent oils are tested
employed for further evaluation. Such tests can be run concurrently. At the discretion of the interested parties, the
concurrently, if desired. testing may be continued even after an incompatible test result
is observed.
5. Significance and Use
7.2 Preparation of Mixtures—Prepare mixtures similarly,
5.1 The compatibility of oils can be important for users of
regardless of whether one or three mixtures of differing ratios
oil-lubricated equipment. Mixing of two oils can produce a
will be tested sequentially or concurrently.
substance markedly inferior to either of its constituent materi-
7.2.1 Blend a fresh mixture of the two oils to be evaluated
als. One or more of the following can occur:
for compatibility (neat, constituent oils are designated A and
5.1.1 A mixture of incompatible oils most often forms a
B). Determine the amounts to be mixed from the amount of oil
precipitate. The precipitate will form unwanted deposits in the
required by the tests. Blend at least 10 % more mixture than is
lubrication system, plug filters, and oil passageways.
actually needed for the tests. Do not blend more than can be
5.1.2 Amixture of incompatible oils will sometimes exhibit
used immediately. No more than 7 days should elapse between
degradation of certain performance parameters like
mixture preparation and the start of any test.
demulsibility, foam inhibition oxidation stability, rust protec-
7.2.1.1 For example, one can prepare a 50:50 mixture by
tion ability, or antiwear protection ability.
adding equal amounts 61 % of oils, neat oils A and B, into a
5.1.3 Amixture of incompatible oils will sometimes exhibit
separate clean, dry, glass beaker, and mixing thoroughly.
non-miscibility of the base oils with each other.
7.2.2 Heat the beaker and mixtures in the oven, or appro-
5.1.4 Such incompatibilities can lead to catastrophic equip-
priate heating assembly, at 65 °C 6 3 °C for a minimum of
ment failures.
23 h to 25 h with occasional mixing before completing the
5.2 To minimize the chances of these problems occurring,
mixing procedure.
lubricant suppliers recommend evaluating compatibility of
NOTE 1—Test Method D7843 has taught us the sample shall be heated
lubricating oil of different formulations and sources prior to
for 23 h to 25 h for proper incorporation of the insoluble components.
mixing. Equipment users most often do not have the resources
to evaluate oil compatibility and must rely on their suppliers.
7.2.3 After the blending procedure is complete, the user
Mixing of oils without first determining the compatibility is a
may continue heating the sample in an oven for the incubation
highly imprudent practice.
time or instead, not heat and store at room temperature for the
incubation time.
5.3 Although new turbine oils may be compatible, in-
service oil of the same type may be degraded or contaminated
NOTE 2—The storage temperature needs to be agreed between the
to such an extent that the new oil added may not be compatible
parties involved.
with the system oil. In-service oil compatibility with new oil
7.2.4 However, before testing, a room temperature incuba-
additions should be evaluated on a case-by-case basis.
tion is suggested as described in Test Method D7843, subsec-
5.4 The oxidation resistance of different oils of the same
tion 8.2, stored between 15 °C to 25 °C, away from UV light
type can vary widely, and compatibility does not imply
for an incubation period of 68 h to 76 h.
equivalentperformancewithoutoxidationperformancetesting.
NOTE 3—Test Method D7843 testing has taught that the proper
formation of varnish particles requires this incubation period condition.
6. Apparatus
Many examples have reported no insoluble material formed directly after
6.1 The equipment and materials required for this practice the heating cycle.
shall be those required by the test methods used to evaluate
7.3 Tier 1 Testing—This is the first series of evaluation for
compatibility.
the oils. The properly blended oils (Section 7.2) may be tested
6.1.1 Laboratory Oven, static-air or stirred-air type, capable
using the recommended Tier 1 tests.
ofmaintainingthetesttemperaturewithin 63 °Candequipped
7.3.1 Observe the oil in accordance with Appendix X1.If
with one or more grill-type wire shelves.
the oils display an incompatible result, conclude the test and
6.1.2 Laboratory Cooler, capable of maintaining the test
report in accordance with Section 8.
temperature within 63 °C.
6.1.3 Reflector Flood Lamp, 150 W.
7.4 Tier 2 Testing—This is the second series of evaluation
for the oils. The properly blended oils (Section 7.2) may be
7. Procedure
tested using the recommended Tier 2 tests.
7.1 Testing is conducted (see Section 7.3 – 7.6) for mixture 7.4.1 Compatibility issues of oils can have their root cause
proportions as agreed upon with the test requestor or user and through the variation of interfacial forces of the fluid: liquid-
dependent on the available sample volumes supplied. Either liquid (Test Method D1401), liquid-gas (Test Method D892)
the sequential testing protocol described in Option 1 or the and liquid-solid (Test Method D7843). For that reason, inter-
concurrent testing protocol described in Option 2 can be used. facial tests are recommended to be included as a part of
D7155 − 20
required testing. When oils are blended the lack of compatibil- amount greater than repeatability of the test method. Record as
ity is accentuated at the fluid surfaces. Measuring these incompatible or fail if the foaming characteristic is worse
interfacial properties provides a closer look at the fluid (more) than the constituent oils by an amount greater than
interactions and demonstrate the oil compatibility or lack of repeatability of the test.
compatibility. Many times, the changes in these interface
7.4.3.1 Air Release Properties—Determine and record the
properties are the cause of changes in other properties.
air release property as described in Test Methods D3427.
7.4.3.2 Air release is another example of the measurement
NOTE 4—Use great care when preparing the contents of the beaker for
some tests. Semi-solid material not visible to the unaided eye may have of the liquid-air interface property. Due to its measurement
settled to the bottom of the vessel. This material needs to be thoroughly
complexity, it is not typically considered a Tier 2 test but it
mixed back into the sample prior to testing for insolubles.
couldaugmentfoamasanair-liquidtestifdesired.Themixture
7.4.2 Membrane Patch Colorimetry Test (MPC)— is considered to be compatible if the air release properties of
Determine and record the membrane patch test results as the mixture are equal to or better (lower air release time) than
described in Test Method D7843. Varnish production or in- either constituent oil. Record as compatible or pass if the air
soluble formation is a measurement of oil compatibility. The
release property of the mixture is equal to or better than the
Tier 1 visual testing is a crude visual measurement of this constituent oils by an amount greater than repeatability of the
property. In many cases the amount of the insoluble is too
test method. Record as incompatible or fail if the air release
small to be observed visually. For this reason, it is recom- property of the mixture is worse (higher air release time) than
mended to test the oil by Test Method D7843 (MPC testing).
the constituent oils by an amount greater than repeatability of
The formation of solids (insoluble or varnish) is a physical the test.
measure of the liquid to solid interface. Oil incompatibility
7.4.3.3 There needs to be an agreement between the parties
shows changes in the liquid-solid interface more frequently
involved as to the measurement test method of the air-liquid
than many other properties. A blend of the oils that shows an
property test.
increase in the MPC values is considered failing this test.
7.4.4 Water Separability—Determine and record the water
Record as compatible or pass if the insoluble content of the
separability results as described in Test Method D1401. Water
mixture is the same or lower than both of the constituent oils
separation(demulsibility)isameasurementoftheliquid-liquid
by an amount greater than repeatability of the test method.
interface property. The liquid-liquid interface property is the
Record as incompatible or fail if the insoluble content of the
third interface property that shows a high degree of sensitivity
mixture is greater than the larger of the two constituent oils by
to oils compatibility. The mixture is considered to be compat-
an amount greater than repeatability of the test.
ible if the water separability of the mixture is equal to or better
7.4.2.1 Pentane Insolubles—Determine the pentane in-
(lowerdemulsibilitytime)thaneitherconstituentoil.Recordas
solublecontentusingTestMethodD893.SimilartotheD7843,
compatible or pass if the water separability of the mixture is
the pentane insoluble test is a measure of the liquid-solid
better than the constituent oils by an amount greater than
interface and could be considered a basic Tier 2 test as well.
repeatability of the test method, Record as incompatible or fail
The mixture is considered to be compatible if the pentane
if the water separability of the mixture is worse (higher
insoluble content of the mixture is equal to or less than either
demulsibility time) than the constituent oils by an amount
constituent oil. Record as compatible or pass if the insoluble
greater than the repeatability of the test method.
content of the mixture is the same or lower than both of the
NOTE 5—If one of the oils is an in-service oil the test results on the
constituent oils
...
This document is not an ASTM standard and is intended only to provide the user of an ASTM standard an indication of what changes have been made to the previous version. Because
it may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current version
of the standard as published by ASTM is to be considered the official document.
Designation: D7155 − 18 D7155 − 20
Standard Practice for
Evaluating Compatibility of Mixtures of Turbine Lubricating
Oils
This standard is issued under the fixed designation D7155; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope*
1.1 This practice covers the compatibility of mixtures of turbine lubricating oils as defined by Specification D4304. The
methods compare properties of specific mixtures with those of the neat oils after storage at specified conditions.
1.2 The methods are grouped into four tiers of testing types:
1.2.1 Tier 1—Visual appearance
1.2.2 Tier 2—Interfacial properties
1.2.3 Tier 3—Physical and chemical properties
1.2.4 Tier 4—Specific performance properties
1.3 The methods can be used to evaluate new (unused) lubricant compatibility or the effects of adding new (unused) lubricant
to in-service lubricant in the system.
1.4 This practice does not evaluate the wear prevention characteristics, load carrying capacity, or the mechanical shear stability
of lubricants mixtures while in service. If anti-wear (AW), extreme pressure (EP), or shear stability are to be evaluated, further
testing of these parameters may be required.
1.5 Mixtures of the two constituent oils are evaluated using the Tier 1 and Tier 2 testing protocol. Sequential or concurrent
testing is continued by applying tests from Tier 3 or Tier 4 until the test requestor or user is satisfied that the intent of this practice
has been met. If any mixture fails the methods, the oils are considered incompatible by that method. If all mixtures pass the
methods, the oils are considered compatible by those methods. It is recommended that passing only Tier 1 does not adequately test
for fluid compatibility.
1.6 If the mixture passes Tier 1, it shows two oils are visually compatible only. If the mixture passes Tier 1 and 2, it shows two
oils are visually and interfacially compatible. If the mixture passes Tier 1, 2 and 3, it shows two oils are visually, interfacially,
physically, and chemically compatible. If the mixture passes Tier 1, 2, 3, 4, it shows two oils are compatible with the highest
confidence level. Testing each tier level is giving the user more confidence that the two fluids are compatible.
1.7 This practice applies only to lubricating oils having characteristics suitable for evaluation by the suggested test methods.
If the scope of a specific test method limits testing to those oils within a specified range of properties, oils outside that range cannot
be tested for compatibility by that test method.
1.8 This practice may be used to evaluate the compatibility of different types and grades of oil. However, it is not intended to
evaluate such mixtures for lubrication performance. The user is advised to consult with suppliers in these situations.
1.9 This practice does not purport to cover all test methods that could be employed.
1.10 The values stated in SI units are to be regarded as standard. The values given in parentheses after SI units are provided
for information only and are not considered standard.
1.11 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility
of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of
regulatory limitations prior to use.
1.12 This international standard was developed in accordance with internationally recognized principles on standardization
established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued
by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
This practice is under the jurisdiction of ASTM Committee D02 on Petroleum Products, Liquid Fuels, and Lubricants and is the direct responsibility of Subcommittee
D02.C0.01 on Turbine Oil Monitoring, Problems and Systems.
Current edition approved June 1, 2018May 1, 2020. Published August 2018June 2020. Originally approved in 2006. Last previous edition approved in 20112018 as
D7155 – 11.D7155 – 18. DOI: 10.1520/D7155-18.10.1520/D7155-20.
*A Summary of Changes section appears at the end of this standard
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D7155 − 20
2. Referenced Documents
2.1 ASTM Standards:
D130 Test Method for Corrosiveness to Copper from Petroleum Products by Copper Strip Test
D445 Test Method for Kinematic Viscosity of Transparent and Opaque Liquids (and Calculation of Dynamic Viscosity)
D611 Test Methods for Aniline Point and Mixed Aniline Point of Petroleum Products and Hydrocarbon Solvents
D664 Test Method for Acid Number of Petroleum Products by Potentiometric Titration
D665 Test Method for Rust-Preventing Characteristics of Inhibited Mineral Oil in the Presence of Water
D892 Test Method for Foaming Characteristics of Lubricating Oils
D893 Test Method for Insolubles in Used Lubricating Oils
D974 Test Method for Acid and Base Number by Color-Indicator Titration
D1401 Test Method for Water Separability of Petroleum Oils and Synthetic Fluids
D1500 Test Method for ASTM Color of Petroleum Products (ASTM Color Scale)
D2270 Practice for Calculating Viscosity Index from Kinematic Viscosity at 40 °C and 100 °C
D2272 Test Method for Oxidation Stability of Steam Turbine Oils by Rotating Pressure Vessel
D3120 Test Method for Trace Quantities of Sulfur in Light Liquid Petroleum Hydrocarbons by Oxidative Microcoulometry
D3427 Test Method for Air Release Properties of Hydrocarbon Based Oils
D4175 Terminology Relating to Petroleum Products, Liquid Fuels, and Lubricants
D4304 Specification for Mineral and Synthetic Lubricating Oil Used in Steam or Gas Turbines
D4310 Test Method for Determination of Sludging and Corrosion Tendencies of Inhibited Mineral Oils
D4629 Test Method for Trace Nitrogen in Liquid Hydrocarbons by Syringe/Inlet Oxidative Combustion and Chemiluminescence
Detection
D5185 Test Method for Multielement Determination of Used and Unused Lubricating Oils and Base Oils by Inductively
Coupled Plasma Atomic Emission Spectrometry (ICP-AES)
D5762 Test Method for Nitrogen in Liquid Hydrocarbons, Petroleum and Petroleum Products by Boat-Inlet Chemiluminescence
D5846 Test Method for Universal Oxidation Test for Hydraulic and Turbine Oils Using the Universal Oxidation Test Apparatus
D6186 Test Method for Oxidation Induction Time of Lubricating Oils by Pressure Differential Scanning Calorimetry (PDSC)
D6304 Test Method for Determination of Water in Petroleum Products, Lubricating Oils, and Additives by Coulometric Karl
Fischer Titration
D6514 Test Method for High Temperature Universal Oxidation Test for Turbine Oils
D7042 Test Method for Dynamic Viscosity and Density of Liquids by Stabinger Viscometer (and the Calculation of Kinematic
Viscosity)
D7843 Test Method for Measurement of Lubricant Generated Insoluble Color Bodies in In-Service Turbine Oils using
Membrane Patch Colorimetry
D7873 Test Method for Determination of Oxidation Stability and Insolubles Formation of Inhibited Turbine Oils at 120 °C
Without the Inclusion of Water (Dry TOST Method)
D8148 Test Method for Spectroscopic Determination of Haze in Fuels
3. Terminology
3.1 For definitions of terms used in this test method, refer to Terminology D4175.
3.2 Definitions of Terms Specific to This Standard:
3.2.1 compatibility, n—of lubricating oils, the ability of lubricating oils to mix together without significant degradation of
properties or performance.
3.2.1.1 Discussion—
When a mixture of two oils has properties or performance significantly inferior to either of the constituent oils, then the two oils
are incompatible. If the properties are inferior to those of one neat oil but not inferior to those of the other, then such is not
necessarily considered an indication of incompatibility. To be considered significantly inferior, the property of the mixture would
be worse than the poorer of the two neat oils by an amount exceeding the repeatability (or in the case of third party verification
testing, the reproducibility) of the test method used to evaluate the property. (See the definitions for fail and pass.)
3.2.2 fail, n—in compatibility testing of oil mixtures, a test result that is inferior to that of the poorer of the two constituent oils
by an amount exceeding the repeatability of the test method used for the evaluation.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM Standards
volume information, refer to the standard’s Document Summary page on the ASTM website.
D7155 − 20
3.2.3 insolubles, n—solids or semi-solid material that accumulate on the bottom of a liquid. As broadened, insolubles include
varnishes and “non-sedimentatious materials” resulting from fluid incompatibility that change the appearance of a bright and clear
liquid to “hazy” or “cloudy.”
3.2.4 pass, n—in compatibility testing of oil mixtures, a test result that is equal to or better than that of the poorer of the two
constituent oils by an amount exceeding the repeatability of the test method used for the evaluation.
3.2.5 type and grade, n—type and grade refer to lubricants of the same general type such as Rust and Oxidation Inhibited turbine
oil (R&O) and ISO Viscosity grades.
3.2.6 10:90 mixture, n—a uniform blend of 10 % by volume of one oil with 90 % by volume of a second oil.
3.2.7 50:50 mixture, n—a uniform blend of 50 % by volume of each of two component oils.
3.2.8 90:10 mixture, n—a uniform blend of 90 % by volume of one oil with 10 % by volume of a second oil.
4. Summary of Practice
4.1 Option 1—Prepare a 50:50 mixture of two oils to be evaluated for compatibility. This mixture and the two neat, constituent
oils are tested using the compatibility tests. Depending on the performance of the mixture, relative to those of the constituent oils,
10:90 and 90:10 mixtures may need to be tested in addition.
4.2 Option 2—Instead of testing mixtures in sequential order, 10:90 and 90:10 mixtures are tested at the same time the 50:50
mixture is evaluated. If all mixtures pass Tier 1 and 2 compatibility tests, or if the application requires the evaluation of specific
properties, Tier 3 and 4 compatibility tests can be employed for further evaluation. Such tests can be run concurrently, if desired.
5. Significance and Use
5.1 The compatibility of oils can be important for users of oil-lubricated equipment. Mixing of two oils can produce a substance
markedly inferior to either of its constituent materials. One or more of the following can occur:
5.1.1 A mixture of incompatible oils most often forms a precipitate. The precipitate will form unwanted deposits in the
lubrication system, plug filters, and oil passageways.
5.1.2 A mixture of incompatible oils will sometimes exhibit degradation of certain performance parameters like demulsibility,
foam inhibition oxidation stability, rust protection ability, or antiwear protection ability.
5.1.3 A mixture of incompatible oils will sometimes exhibit non-miscibility of the base oils with each other.
5.1.4 Such incompatibilities can lead to catastrophic equipment failures.
5.2 To minimize the chances of these problems occurring, lubricant suppliers recommend evaluating compatibility of
lubricating oil of different formulations and sources prior to mixing. Equipment users most often do not have the resources to
evaluate oil compatibility and must rely on their suppliers. Mixing of oils without first determining the compatibility is a highly
imprudent practice.
5.3 Although new turbine oils may be compatible, in-service oil of the same type may be degraded or contaminated to such an
extent that the new oil added may not be compatible with the system oil. In-service oil compatibility with new oil additions should
be evaluated on a case-by-case basis.
5.4 The oxidation resistance of different oils of the same type can vary widely, and compatibility does not imply equivalent
performance without oxidation performance testing.
6. Apparatus
6.1 The equipment and materials required for this practice shall be those required by the test methods used to evaluate
compatibility.
6.1.1 Laboratory Oven, static-air or stirred-air type, capable of maintaining the test temperature within 63 °C and equipped
with one or more grill-type wire shelves.
6.1.2 Laboratory Cooler, capable of maintaining the test temperature within 63 °C.
6.1.3 Reflector Flood Lamp, 150 W.
7. Procedure
7.1 Testing is conducted (see Section 7.3 – 7.6) for mixture proportions as agreed upon with the test requestor or user and
dependent on the available sample volumes supplied. Either the sequential testing protocol described in Option 1 or the concurrent
testing protocol described in Option 2 can be used. Using Option 1, a 50:50 mixture and the two constituent oils are tested. If this
mixture is found compatible, 10:90 and 90:10 mixtures which reflect drain-and fill conversion or make up proportions may be
tested. Using Option 2, all mixtures (10:90, 50:50, and 90:10) and the two constituent oils are tested concurrently. At the discretion
of the interested parties, the testing may be continued even after an incompatible test result is observed.
7.2 Preparation of Mixtures—Prepare mixtures similarly, regardless of whether one or three mixtures of differing ratios will be
tested sequentially or concurrently.
D7155 − 20
7.2.1 Blend a fresh mixture of the two oils to be evaluated for compatibility (neat, constituent oils are designated A and B).
Determine the amounts to be mixed from the amount of oil required by the tests. Blend at least 10 % more mixture than is actually
needed for the tests. Do not blend more than can be used immediately. No more than 7 days should elapse between mixture
preparation and the start of any test.
7.2.1.1 For example, one can prepare a 50:50 mixture by adding equal amounts 61 % of oils, neat oils A and B, into a separate
clean, dry, glass beaker, and mixing thoroughly.
7.2.2 Heat the beaker and mixtures in the oven, or appropriate heating assembly, at 65 °C 6 3 °C for a minimum of 23 h to 25 h
with occasional mixing before completing the mixing procedure.
NOTE 1—Test Method D7843 has taught us the sample shall be heated for 23 h to 25 h for proper incorporation of the insoluble components.
7.2.3 After the blending procedure is complete, the user may continue heating the sample in an oven for the incubation time
or instead, not heat and store at room temperature for the incubation time.
NOTE 2—The storage temperature needs to be agreed between the parties involved.
7.2.4 However, before testing, a room temperature incubation is suggested as described in Test Method D7843, subsection 8.2,
stored between 15 °C to 25 °C, away from UV light for an incubation period of 68 h to 76 h.
NOTE 3—Test Method D7843 testing has taught that the proper formation of varnish particles requires this incubation period condition. Many examples
have reported no insoluble material formed directly after the heating cycle.
7.3 Tier 1 Testing—This is the first series of evaluation for the oils. The properly blended oils (Section 7.2) may be tested using
the recommended Tier 1 tests.
7.3.1 Observe the oil in accordance with Appendix X1. If the oils display an incompatible result, conclude the test and report
in accordance with Section 8.
7.4 Tier 2 Testing—This is the second series of evaluation for the oils. The properly blended oils (Section 7.2) may be tested
using the recommended Tier 2 tests.
7.4.1 Compatibility issues of oils can have their root cause through the variation of interfacial forces of the fluid: liquid-liquid
(Test Method D1401), liquid-gas (Test Method D892) and liquid-solid (Test Method D7843). For that reason, interfacial tests are
recommended to be included as a part of required testing. When oils are blended the lack of compatibility is accentuated at the
fluid surfaces. Measuring these interfacial properties provides a closer look at the fluid interactions and demonstrate the oil
compatibility or lack of compatibility. Many times, the changes in these interface properties are the cause of changes in other
properties.
NOTE 4—Use great care when preparing the contents of the beaker for some tests. Semi-solid material not visible to the unaided eye may have settled
to the bottom of the vessel. This material needs to be thoroughly mixed back into the sample prior to testing for insolubles.
7.4.2 Membrane Patch Colorimetry Test (MPC)—Determine and record the membrane patch test results as described in Test
Method D7843. Varnish production or insoluble formation is a measurement of oil compatibility. The Tier 1 visual testing is a crude
visual measurement of this property. In many cases the amount of the insoluble is too small to be observed visually. For this reason,
it is recommended to test the oil by Test Method D7843 (MPC testing). The formation of solids (insoluble or varnish) is a physical
measure of the liquid to solid interface. Oil incompatibility shows changes in the liquid-solid interface more frequently than many
other properties. A blend of the oils that shows an increase in the MPC values is considered failing this test. Record as compatible
or pass if the insoluble content of the mixture is the same or lower than both of the constituent oils by an amount greater than
repeatability of the test method. Record as incompatible or fail if the insoluble content of the mixture is greater than the larger of
the two constituent oils by an amount greater than repeatability of the test.
7.4.2.1 Pentane Insolubles—Determine the pentane insoluble content using Test Method D893. Similar to the D7843, the
pentane insoluble test is a measure of the liquid-solid interface and could be considered a basic Tier 2 test as well. The mixture
is considered to be compatible if the pentane insoluble content of the mixture is equal to or less than either constituent oil. Record
as compatible or pass if the insoluble content of the mixture is the same or lower than both of the constituent oils by an amount
greater than repeatability of the test method. Record as incompatible or fail if the insoluble content of the mixture is greater than
the larger of the two constituent oils by an amount greater than repeatability of the test.
7.4.2.2 Test Method D7843 is more sensitive to low levels of varnish formation than Test Method D893. There needs to be an
agreement between the parties involved as to the measurement test method of the insoluble content.
7.4.3 Foaming Characteristics—Determine and record the foaming characteristic as described in Test Method D892. Sequence
I foam testing is the recommended procedure. Foam is an example of the measurement of the liquid-air interface property. Like
insoluble material formation and the liquid-solid property, the air-liquid property is one of those properties very sensitive to oil
incompatibility. Degradation of this property is one of the first observed between incompatible oils. The mixture is considered to
be compatible if the foaming characteristic of the mixture is equal to or less than either constituent oil. Record as compatible or
pass if the foaming characteristic of the mixture is better (less) than the constituent oils by an amount greater than repeatability
of the test method. Record as incompatible or fail if the foaming characteristic is worse (more) than the constituent oils by an
amount greater than repeatability of the test.
7.4.3.1 Air Release Properties—Determine and record the air release property as described in Test Methods D3427.
D7155 − 20
7.4.3.2 Air release is another example of the measurement of the liquid-air interface property. Due to its measurement
complexity, it is not typically considered a Tier 2 test but it could augment foam as an air-liquid test if desired. The mixture is
considered to be compatible if the air release properties of the mixture are equal to or better (lower air release time) than either
constituent oil. Record as compatible or pass if the air release property of the mixture is equal to or better than the constituent oils
by an amount greater than repeatability of the
...
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