ASTM D6185-11(2017)
(Practice)Standard Practice for Evaluating Compatibility of Binary Mixtures of Lubricating Greases
Standard Practice for Evaluating Compatibility of Binary Mixtures of Lubricating Greases
SIGNIFICANCE AND USE
5.1 The compatibility of greases can be important for users of grease-lubricated equipment. It is well known that the mixing of two greases can produce a substance markedly inferior to either of its constituent materials. One or more of the following can occur. A mixture of incompatible greases most often softens, sometimes excessively. Occasionally, it can harden. In extreme cases, the thickener and liquid lubricant will completely separate. Bleeding can be so severe that the mixed grease will run out of an operating bearing. Excessive syneresis can occur, forming pools of liquid lubricant separated from the grease. Dropping points can be reduced to the extent that grease or separated oil runs out of bearings at elevated operating temperatures. Such events can lead to catastrophic lubrication failures.
5.1.1 Because of such occurrences, equipment manufacturers recommend completely cleaning the grease from equipment before installing a different grease. Service recommendations for grease-lubricated equipment frequently specify the caveat–do not mix greases under any circumstances. Despite this admonition, grease mixing will occur and, at times, cannot be avoided. In such instances, it would be useful to know whether the mixing of two greases could lead to inadequate lubrication with disastrous consequences. Equipment users most often do not have the resources to evaluate grease compatibility and must rely on their suppliers. Mixing of greases is a highly imprudent practice. Grease and equipment manufacturers alike recognize such practices will occur despite all warnings to the contrary. Thus, both users and suppliers have a need to know the compatibility characteristics of the greases in question.
5.2 There are two approaches to evaluating the compatibility of grease mixtures. One is to determine whether such mixtures meet the same specification requirements as the constituent components. This approach is not addressed by this practice. Instead, this practice...
SCOPE
1.1 This practice covers a protocol for evaluating the compatibility of one or three binary mixtures of lubricating greases by comparing their properties or performance relative to those of the neat greases comprising the mixture.
1.2 Three properties are evaluated in a primary testing protocol using standard test methods: (1) dropping point by Test Method D566 (or Test Method D2265); (2) shear stability by Test Methods D217, 100 000–stroke worked penetration; and (3) storage stability at elevated-temperature by change in 60-stroke penetration (Test Method D217). For compatible mixtures (those passing all primary testing), a secondary (nonmandatory) testing scheme is suggested when circumstances indicate the need for additional testing.
1.3 Sequential or concurrent testing is continued until the first failure. If any mixture fails any of the primary tests, the greases are incompatible. If all mixtures pass the three primary tests, the greases are considered compatible.
1.4 This practice applies only to lubricating greases having characteristics suitable for evaluation by the suggested test methods. If the scope of a specific test method limits testing to those greases within a specified range of properties, greases outside that range cannot be tested for compatibility by that test method. An exception to this would be when the tested property of the neat, constituent greases is within the specified range, but the tested property of a mixture is outside the range because of incompatibility.
1.5 This practice does not purport to cover all test methods that could be employed.
1.6 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.
1.7 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 env...
General Information
- Status
- Published
- Publication Date
- 14-Dec-2017
- Technical Committee
- D02 - Petroleum Products, Liquid Fuels, and Lubricants
- Drafting Committee
- D02.G0.01 - Chemical and General Laboratory Tests
Relations
- 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
- Refers
ASTM D4175-23e1 - Standard Terminology Relating to Petroleum Products, Liquid Fuels, and Lubricants - Effective Date
- 01-Jul-2023
- Effective Date
- 01-Jun-2020
- Effective Date
- 01-Jun-2020
- Effective Date
- 01-Jun-2020
- Effective Date
- 01-May-2020
- Refers
ASTM D1742-20 - Standard Test Method for Oil Separation from Lubricating Grease During Storage - Effective Date
- 01-May-2020
- Effective Date
- 01-May-2020
- Effective Date
- 01-Apr-2020
- Effective Date
- 01-Feb-2020
- Effective Date
- 01-Dec-2019
- Effective Date
- 01-Nov-2019
- Effective Date
- 01-Nov-2019
Overview
ASTM D6185-11(2017): Standard Practice for Evaluating Compatibility of Binary Mixtures of Lubricating Greases provides a standardized protocol for assessing the compatibility of two-component grease mixtures. The compatibility of greases is a crucial concern for users of grease-lubricated equipment. Mixing incompatible greases can lead to significant performance degradation, such as excessive softening or hardening, oil separation (bleeding or syneresis), reduced dropping point, and in severe cases, catastrophic lubrication failure.
ASTM D6185 is used globally in industrial, automotive, and equipment maintenance sectors to minimize the risk of equipment damage caused by unintended grease mixing. By following this practice, both suppliers and end-users can determine whether two greases may be safely combined or if a complete grease changeover procedure is required.
Key Topics
- Binary Mixture Compatibility: The practice focuses on evaluating the compatibility of mixtures consisting of two greases (binary mixtures). It assesses if mixing leads to property changes that compromise grease performance.
- Primary Testing Protocol: The standard mandates testing three critical properties of neat greases and their mixtures:
- Dropping point (ASTM D566 or D2265)
- Shear stability (100,000-stroke worked penetration, ASTM D217)
- Storage stability at elevated temperature (change in 60-stroke penetration, ASTM D217)
- Assessment Procedure: Mixtures are tested sequentially or concurrently in 50:50, 10:90, and 90:10 mass ratios. If any mixture fails any primary test, the greases are deemed incompatible.
- Secondary (Optional) Testing: If primary tests are passed but further evaluation is needed, additional properties relevant to the application (such as wear, corrosion, or resistance to water washout) may be tested using referenced methods.
- Reporting: Results include the identification of tested greases, mix ratios, and compatibility outcomes for each test.
Applications
ASTM D6185-11(2017) is widely applied in:
- Industrial Maintenance and Reliability: Preventing failures caused by grease incompatibility in bearings, gears, and other machinery.
- Automotive and Transportation: Ensuring safe grease changeovers in fleet maintenance and repair operations.
- Equipment Manufacturing: Advising end-users and maintenance teams about approved grease combinations or necessary precautions during lubricant replacement.
- Lubricant Quality Assurance: Used by lubricant manufacturers and suppliers to demonstrate compatibility of product lines or formulate blending recommendations.
- Condition-Based Monitoring: Integrating compatibility assessments into predictive maintenance strategies to minimize downtime and extend equipment life.
Practical value: This standard helps prevent costly machine breakdowns, reduces maintenance risks, and supports the development of maintenance procedures where grease mixing could occur-either intentionally or accidentally.
Related Standards
- ASTM D217: Test Methods for Cone Penetration of Lubricating Grease
- ASTM D566 / D2265: Test Methods for Dropping Point of Lubricating Grease
- ASTM D4950: Classification and Specification for Automotive Service Greases
- ASTM D1264: Water Washout Characteristics of Lubricating Greases
- ASTM D1742 / D4425: Oil Separation from Lubricating Grease
- ASTM D1831 / D3336: Roll Stability and Bearing Life of Lubricating Grease
Keywords: grease compatibility, binary mixtures, lubricating grease, ASTM D6185, lubrication failure, dropping point, penetration, shear stability, oil separation, grease testing, equipment maintenance.
By adhering to ASTM D6185, organizations can significantly reduce the operational risks associated with grease mixing, ensuring optimal equipment reliability and maintenance safety.
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Frequently Asked Questions
ASTM D6185-11(2017) is a standard published by ASTM International. Its full title is "Standard Practice for Evaluating Compatibility of Binary Mixtures of Lubricating Greases". This standard covers: SIGNIFICANCE AND USE 5.1 The compatibility of greases can be important for users of grease-lubricated equipment. It is well known that the mixing of two greases can produce a substance markedly inferior to either of its constituent materials. One or more of the following can occur. A mixture of incompatible greases most often softens, sometimes excessively. Occasionally, it can harden. In extreme cases, the thickener and liquid lubricant will completely separate. Bleeding can be so severe that the mixed grease will run out of an operating bearing. Excessive syneresis can occur, forming pools of liquid lubricant separated from the grease. Dropping points can be reduced to the extent that grease or separated oil runs out of bearings at elevated operating temperatures. Such events can lead to catastrophic lubrication failures. 5.1.1 Because of such occurrences, equipment manufacturers recommend completely cleaning the grease from equipment before installing a different grease. Service recommendations for grease-lubricated equipment frequently specify the caveat–do not mix greases under any circumstances. Despite this admonition, grease mixing will occur and, at times, cannot be avoided. In such instances, it would be useful to know whether the mixing of two greases could lead to inadequate lubrication with disastrous consequences. Equipment users most often do not have the resources to evaluate grease compatibility and must rely on their suppliers. Mixing of greases is a highly imprudent practice. Grease and equipment manufacturers alike recognize such practices will occur despite all warnings to the contrary. Thus, both users and suppliers have a need to know the compatibility characteristics of the greases in question. 5.2 There are two approaches to evaluating the compatibility of grease mixtures. One is to determine whether such mixtures meet the same specification requirements as the constituent components. This approach is not addressed by this practice. Instead, this practice... SCOPE 1.1 This practice covers a protocol for evaluating the compatibility of one or three binary mixtures of lubricating greases by comparing their properties or performance relative to those of the neat greases comprising the mixture. 1.2 Three properties are evaluated in a primary testing protocol using standard test methods: (1) dropping point by Test Method D566 (or Test Method D2265); (2) shear stability by Test Methods D217, 100 000–stroke worked penetration; and (3) storage stability at elevated-temperature by change in 60-stroke penetration (Test Method D217). For compatible mixtures (those passing all primary testing), a secondary (nonmandatory) testing scheme is suggested when circumstances indicate the need for additional testing. 1.3 Sequential or concurrent testing is continued until the first failure. If any mixture fails any of the primary tests, the greases are incompatible. If all mixtures pass the three primary tests, the greases are considered compatible. 1.4 This practice applies only to lubricating greases having characteristics suitable for evaluation by the suggested test methods. If the scope of a specific test method limits testing to those greases within a specified range of properties, greases outside that range cannot be tested for compatibility by that test method. An exception to this would be when the tested property of the neat, constituent greases is within the specified range, but the tested property of a mixture is outside the range because of incompatibility. 1.5 This practice does not purport to cover all test methods that could be employed. 1.6 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard. 1.7 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 env...
SIGNIFICANCE AND USE 5.1 The compatibility of greases can be important for users of grease-lubricated equipment. It is well known that the mixing of two greases can produce a substance markedly inferior to either of its constituent materials. One or more of the following can occur. A mixture of incompatible greases most often softens, sometimes excessively. Occasionally, it can harden. In extreme cases, the thickener and liquid lubricant will completely separate. Bleeding can be so severe that the mixed grease will run out of an operating bearing. Excessive syneresis can occur, forming pools of liquid lubricant separated from the grease. Dropping points can be reduced to the extent that grease or separated oil runs out of bearings at elevated operating temperatures. Such events can lead to catastrophic lubrication failures. 5.1.1 Because of such occurrences, equipment manufacturers recommend completely cleaning the grease from equipment before installing a different grease. Service recommendations for grease-lubricated equipment frequently specify the caveat–do not mix greases under any circumstances. Despite this admonition, grease mixing will occur and, at times, cannot be avoided. In such instances, it would be useful to know whether the mixing of two greases could lead to inadequate lubrication with disastrous consequences. Equipment users most often do not have the resources to evaluate grease compatibility and must rely on their suppliers. Mixing of greases is a highly imprudent practice. Grease and equipment manufacturers alike recognize such practices will occur despite all warnings to the contrary. Thus, both users and suppliers have a need to know the compatibility characteristics of the greases in question. 5.2 There are two approaches to evaluating the compatibility of grease mixtures. One is to determine whether such mixtures meet the same specification requirements as the constituent components. This approach is not addressed by this practice. Instead, this practice... SCOPE 1.1 This practice covers a protocol for evaluating the compatibility of one or three binary mixtures of lubricating greases by comparing their properties or performance relative to those of the neat greases comprising the mixture. 1.2 Three properties are evaluated in a primary testing protocol using standard test methods: (1) dropping point by Test Method D566 (or Test Method D2265); (2) shear stability by Test Methods D217, 100 000–stroke worked penetration; and (3) storage stability at elevated-temperature by change in 60-stroke penetration (Test Method D217). For compatible mixtures (those passing all primary testing), a secondary (nonmandatory) testing scheme is suggested when circumstances indicate the need for additional testing. 1.3 Sequential or concurrent testing is continued until the first failure. If any mixture fails any of the primary tests, the greases are incompatible. If all mixtures pass the three primary tests, the greases are considered compatible. 1.4 This practice applies only to lubricating greases having characteristics suitable for evaluation by the suggested test methods. If the scope of a specific test method limits testing to those greases within a specified range of properties, greases outside that range cannot be tested for compatibility by that test method. An exception to this would be when the tested property of the neat, constituent greases is within the specified range, but the tested property of a mixture is outside the range because of incompatibility. 1.5 This practice does not purport to cover all test methods that could be employed. 1.6 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard. 1.7 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 env...
ASTM D6185-11(2017) 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 D6185-11(2017) has the following relationships with other standards: It is inter standard links to ASTM D4175-23a, ASTM D5706-23, ASTM D5707-23, ASTM D4175-23e1, ASTM D4290-20, ASTM D1403-20b, ASTM D1092-20, ASTM D3336-20, ASTM D1742-20, ASTM D2596-20, ASTM D1403-20a, ASTM D1403-20, ASTM D5707-19, ASTM D1092-19, ASTM D4290-19. Understanding these relationships helps ensure you are using the most current and applicable version of the standard.
ASTM D6185-11(2017) 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: D6185 − 11 (Reapproved 2017)
Standard Practice for
Evaluating Compatibility of Binary Mixtures of Lubricating
Greases
This standard is issued under the fixed designation D6185; 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 responsibility of the user of this standard to establish appro-
priate safety, health, and environmental practices and deter-
1.1 This practice covers a protocol for evaluating the
mine the applicability of regulatory limitations prior to use.
compatibility of one or three binary mixtures of lubricating
For specific safety information, see 7.2.3.
greases by comparing their properties or performance relative
1.8 This international standard was developed in accor-
to those of the neat greases comprising the mixture.
dance with internationally recognized principles on standard-
1.2 Three properties are evaluated in a primary testing
ization established in the Decision on Principles for the
protocol using standard test methods: (1) dropping point by
Development of International Standards, Guides and Recom-
Test Method D566 (or Test Method D2265); (2) shear stability
mendations issued by the World Trade Organization Technical
by Test Methods D217, 100 000-stroke worked penetration;
Barriers to Trade (TBT) Committee.
and (3) storage stability at elevated-temperature by change in
60-stroke penetration (Test Method D217). For compatible
2. Referenced Documents
mixtures (those passing all primary testing), a secondary
2.1 ASTM Standards:
(nonmandatory) testing scheme is suggested when circum-
D217 Test Methods for Cone Penetration of Lubricating
stances indicate the need for additional testing.
Grease
1.3 Sequential or concurrent testing is continued until the
D566 TestMethodforDroppingPointofLubricatingGrease
first failure. If any mixture fails any of the primary tests, the
D972 Test Method for Evaporation Loss of Lubricating
greases are incompatible. If all mixtures pass the three primary
Greases and Oils
tests, the greases are considered compatible.
D1092 Test Method for Measuring Apparent Viscosity of
Lubricating Greases
1.4 This practice applies only to lubricating greases having
D1263 Test Method for Leakage Tendencies of Automotive
characteristics suitable for evaluation by the suggested test
Wheel Bearing Greases (Withdrawn 2010)
methods. If the scope of a specific test method limits testing to
D1264 Test Method for Determining the Water Washout
those greases within a specified range of properties, greases
Characteristics of Lubricating Greases
outsidethatrangecannotbetestedforcompatibilitybythattest
D1403 Test Methods for Cone Penetration of Lubricating
method. An exception to this would be when the tested
Grease Using One-Quarter and One-Half Scale Cone
property of the neat, constituent greases is within the specified
Equipment
range, but the tested property of a mixture is outside the range
D1478 Test Method for Low-Temperature Torque of Ball
because of incompatibility.
Bearing Grease
1.5 This practice does not purport to cover all test methods
D1742 Test Method for Oil Separation from Lubricating
that could be employed.
Grease During Storage
1.6 The values stated in SI units are to be regarded as
D1743 Test Method for Determining Corrosion Preventive
standard. No other units of measurement are included in this
Properties of Lubricating Greases
standard.
D1831 Test Method for Roll Stability of Lubricating Grease
D2265 Test Method for Dropping Point of Lubricating
1.7 This standard does not purport to address all of the
Grease Over Wide Temperature Range
safety concerns, if any, associated with its use. It is the
1 2
This practice is under the jurisdiction ofASTM Committee D02 on Petroleum For referenced ASTM standards, visit the ASTM website, www.astm.org, or
Products, Liquid Fuels, and Lubricants and is the direct responsibility of Subcom- contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
mittee D02.G0.01 on Chemical and General Laboratory Tests. Standards volume information, refer to the standard’s Document Summary page on
Current edition approved Dec. 15, 2017. Published February 2018. Originally the ASTM website.
approved in 1997. Last previous edition approved in 2011 as D6185 – 11. DOI: The last approved version of this historical standard is referenced on
10.1520/D6185-11R17. www.astm.org.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D6185 − 11 (2017)
D2266 Test Method for Wear Preventive Characteristics of 3.1.5 syneresis, n—of lubricating greases, the separation of
Lubricating Grease (Four-Ball Method) liquid lubricant from a lubricating grease due to shrinkage or
D2509 Test Method for Measurement of Load-Carrying rearrangement of the structure.
Capacity of Lubricating Grease (Timken Method) 3.1.5.1 Discussion—Syneresis is a form of bleeding caused
D2595 Test Method for Evaporation Loss of Lubricating
byphysicalorchemicalchangesofthethickness.Separationof
Greases Over Wide-Temperature Range free oil or the formation of cracks that occur in lubricating
D2596 Test Method for Measurement of Extreme-Pressure
greases during storage in containers is most often due to
Properties of Lubricating Grease (Four-Ball Method) syneresis.
D3336 Test Method for Life of Lubricating Greases in Ball
3.1.6 thickener, n—in a lubricating grease, a substance
Bearings at Elevated Temperatures
composed of finely divided particles dispersed in a liquid
D3337 Test Method for Determining Life and Torque of
lubricant to form the product’s structure.
Lubricating Greases in Small Ball Bearings (Withdrawn
3.1.6.1 Discussion—The thickener can be fibers (such as
2009)
various metallic soaps) or plates or spheres (such as certain
D3527 Test Method for Life Performance of Automotive
non-stop thickeners) which are insoluble or, at most, only very
Wheel Bearing Grease
slightly soluble in the liquid lubricant. The general require-
D4049 Test Method for Determining the Resistance of
ments are that the solid particles be extremely small, uniformly
Lubricating Grease to Water Spray
dispersed, and capable of forming a relatively stable, gel-like
D4170 Test Method for Fretting Wear Protection by Lubri-
structure with the liquid lubricant. D217
cating Greases
3.2 Definitions of Terms Specific to This Standard:
D4175 Terminology Relating to Petroleum Products, Liquid
3.2.1 compatibility, n— of lubricating greases, the charac-
Fuels, and Lubricants
teristic of lubricating greases to be mixed together without
D4290 Test Method for Determining the Leakage Tenden-
significant degradation of properties or performance.
cies of Automotive Wheel Bearing Grease Under Accel-
3.2.1.1 Discussion—When a mixture of two greases has
erated Conditions
properties or performance significantly inferior to both of the
D4425 Test Method for Oil Separation from Lubricating
neat, constituent greases, then the two greases are incompat-
Grease by Centrifuging (Koppers Method)
ible.Ifthepropertiesareinferiortothoseofoneneatgreasebut
D4693 TestMethodforLow-TemperatureTorqueofGrease-
not inferior to those of the other, then such is not necessarily
Lubricated Wheel Bearings
considered an indication of incompatibility. To be considered
D4950 Classification and Specification for Automotive Ser-
significantly inferior, the property of the mixture would be
vice Greases
worse than the poorer of the two neat greases by an amount
D5706 Test Method for Determining Extreme Pressure
exceeding the repeatability of the test method used to evaluate
Properties of Lubricating Greases Using a High-
the property (see pass and fail). Incompatibility most often is
Frequency, Linear-Oscillation (SRV) Test Machine
manifested by a degradation in physical properties rather than
D5707 Test Method for Measuring Friction and Wear Prop-
in chemical properties, although, occurrence of the latter is not
erties of Lubricating Grease Using a High-Frequency,
unknown.
Linear-Oscillation (SRV) Test Machine
2.2 Federal Standard:
3.2.2 borderline compatibility, n—of lubricating greases,
Federal Test Method 3467.1 (Standard 791C), Storage Sta-
the characteristic of lubricating greases to be mixed together
bility of Lubricating Grease
with only slight degradation of properties or performance.
3.2.2.1 Discussion—Slight degradation means that the
3. Terminology
propertiesorperformanceofthemixtureispoorerthanthoseof
3.1 Definitions:
the two neat greases but by an amount less than the repeatabil-
3.1.1 bleed (bleeding), n—of lubricating greases, the sepa-
ity of the test method used to evaluate the property. (See
ration of a liquid lubricant from a lubricating grease for any
borderline pass.)
cause.
3.2.3 primary compatibility tests, n—of lubricating greases,
3.1.2 lubricant, n—any material interposed between two
those test methods employed first to evaluate compatibility.
surfacesthatreducesthefrictionorwearbetweenthem. D4175
3.2.3.1 Discussion—The test methods considered the most
significant in the evaluation of grease compatibility, insofar as
3.1.3 lubricating grease, n—a semifluid to solid product of
a dispersion of a thickener in a liquid lubricant. theyprovidethemostinformationwiththeleastexpenditureof
testing resources, include tests for dropping point, consistency
3.1.3.1 Discussion—The dispersion of the thickener forms a
two-phase system and immobilizes the liquid lubricant by (usually softening) after shearing conditions, and consistency
change after storage at elevated temperatures.
surface tension and other physical forces. Other ingredients
imparting special properties are often included. D217
3.2.4 secondary compatibility tests, n—of lubricating
3.1.4 spatulate, v—tomixorblendbyspreadingandfolding greases, those test methods used to evaluate compatibility
with a flat thin, usually metal, tool. when the primary compatibility tests are insufficient or incon-
clusive.
3.2.4.1 Discussion—Such tests are driven by the critical
Available from Standardization Documents Order Desk, Bldg. 4, Section D,
700 Robbins Ave., Philadelphia, PA 19111–5094, Attn: NPODS. features of a given application. For example, if the application
D6185 − 11 (2017)
subjects the grease to water contamination, water washout or 5.1.1 Because of such occurrences, equipment manufactur-
water spray-off tests and, perhaps, corrosion tests would be ersrecommendcompletelycleaningthegreasefromequipment
used for additional evaluation. Secondary compatibility tests before installing a different grease. Service recommendations
are suggested, but not required, by this practice. for grease-lubricated equipment frequently specify the cave-
at–do not mix greases under any circumstances. Despite this
3.2.5 pass, n—in compatibility testing of grease mixtures, a
admonition, grease mixing will occur and, at times, cannot be
test result that is equal to or better than that of the poorer of the
avoided. In such instances, it would be useful to know whether
two constituent greases.
the mixing of two greases could lead to inadequate lubrication
3.2.6 borderline pass, n— in compatibility testing of grease
with disastrous consequences. Equipment users most often do
mixtures, a test result that is inferior to that of the poorer of the
not have the resources to evaluate grease compatibility and
two constituent greases by an amount not exceeding the
must rely on their suppliers. Mixing of greases is a highly
repeatability of the test method used for the evaluation.
imprudent practice. Grease and equipment manufacturers alike
3.2.6.1 Discussion—Borderline pass, borderline fail, bor-
recognize such practices will occur despite all warnings to the
derline compatible, and borderline incompatible are synony-
contrary. Thus, both users and suppliers have a need to know
mous terms.
the compatibility characteristics of the greases in question.
3.2.7 fail, n—in compatibility testing of grease mixtures, a
5.2 There are two approaches to evaluating the compatibil-
test result that is inferior to that of the poorer of the two
ity of grease mixtures. One is to determine whether such
constituentgreasesbyanamountexceedingtherepeatabilityof
mixtures meet the same specification requirements as the
the test method used for the evaluation.
constituent components.This approach is not addressed by this
3.2.8 50:50 mixture, n—auniformblendof50 %bymassof
practice. Instead, this practice takes a specification-
each of two component greases.
independent approach; it describes the evaluation of compat-
3.2.9 10:90 mixture, n—auniformblendof10 %bymassof
ibility on a relative basis using specific test methods.
one grease with 90 % by mass of a second grease.
5.2.1 Three test methods are used because fewer are not
sufficiently definitive. For example, in one study, using
3.2.10 90:10 mixture, n—a uniform blend of 90 % by mass
100 000-stroke worked penetration for evaluation, 62 % of the
of one grease with 10 % by mass of a second grease.
mixtures were judged to be compatible. In a high-temperature
4. Summary of Practice storage stability study, covering a broader spectrum of grease
types, only one-third of the mixtures were compatible. These
4.1 Option 1—A 50:50 mixture of two greases to be
studies used different criteria to judge compatibility.
evaluated for compatibility is prepared by spatulating. This
5.2.2 Compatibility cannot be predicted with certainty from
mixture and the two neat, constituent greases are tested using
foreknowledge of grease composition. Generally, greases hav-
theprimarycompatibilitytests(droppingpoint,100 000-stroke
ing the same or similar thickener types will be compatible.
workedpenetration,andchangein60-strokepenetrationdueto
Uncommonly, even greases of the same type, although nor-
high-temperature storage). Depending on the performance of
mally compatible when mixed, can be incompatible because of
the mixture, relative to those of the constituent greases, 10:90
incompatible additive treatments. Thus, compatibility needs to
and 90:10 mixtures may need to be tested in addition.
be judged on a case-by-case basis.
Alternatively, Option 2 can be used. Instead of testing mixtures
in sequential order, 10:90 and 90:10 mixtures are tested at the
5.3 Two constituent greases are blended in specific ratios.A
same time the 50:50 mixture is evaluated. If all mixtures pass
50:50mixturesimulatesaratiothatmightbeexperiencedwhen
the primary compatibility tests, or if the application requires
one grease (Grease A) is installed in a bearing containing a
the evaluation of specific properties, secondary compatibility
previously installed, different grease (Grease B), and no
tests can be employed for further evaluation. Such tests can be
attemptismadetoflushoutGreaseBwithGreaseA.The10:90
run concurrently, if desired.
and 90:10 ratios are intended to simulate ratios that might
occur when attempts are made to flush out Grease B with
5. Significance and Use
Grease A.
5.1 The compatibility of greases can be important for users
NOTE 1—Some companies evaluate 25:75 and 75:25 ratio mixtures
of grease-lubricated equipment. It is well known that the
instead of 10:90 and 90:10 ratio mixtures. But, the latter two ratios, which
mixing of two greases can produce a substance markedly
are prescribed by this practice, are considered more representative of the
inferiortoeitherofitsconstituentmaterials.Oneormoreofthe flushing practice described in 5.3.
following can occur. A mixture of incompatible greases most
5.3.1 Incompatibility is most often revealed by the evalua-
often softens, sometimes excessively. Occasionally, it can
tion of 50:50 mixtures. However, in some instances 50:50
harden.Inextremecases,thethickenerandliquidlubricantwill
mixtures are compatible and more dilute ratios are incompat-
completely separate. Bleeding can be so severe that the mixed
ible. (See Appendix X1 and Meade. )
greasewillrunoutofanoperatingbearing.Excessivesyneresis
can occur, forming pools of liquid lubricant separated from the
grease. Dropping points can be reduced to the extent that
Myers, E. H., “Incompatibility of Greases,” NLGI Spokesman, April 1983, p.
grease or separated oil runs out of bearings at elevated
24.
operating temperatures. Such events can lead to catastrophic
Meade, F. S., “Compatibility of Greases,” Rock Island Arsenal Laboratory
lubrication failures. Report, No. 56-2405, PB 121731, Aug. 20
...
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