ASTM D5481-21

Standard Test Method for Measuring Apparent Viscosity at High-Temperature and High-Shear Rate by Multicell Capillary Viscometer

SIGNIFICANCE AND USE
5.1 Viscosity is an important property of fluid lubricants. The viscosity of all fluids varies with temperature. Many common petroleum lubricants are non-Newtonian: their viscosity also varies with shear rate. The usefulness of the viscosity of lubricants is greatest when the viscosity is measured at or near the conditions of shear rate and temperature that the lubricants will experience in service.  
5.2 The conditions of shear rate and temperature of this test method are thought to be representative of those in the bearing of automotive engines in severe service.  
5.3 Many equipment manufacturers and lubricant specifications require a minimum high-temperature high-shear viscosity at 150 °C and 106 s−1. The shear rate in capillary viscometers varies across the radius of the capillary. The apparent shear rate at the wall for this test method is increased to compensate for the variable shear rate.3  
5.4 This test was evaluated in an ASTM cooperative program.6
SCOPE
1.1 This test method covers the laboratory determination of high-temperature high-shear (HTHS) viscosity of engine oils at a temperature of 150 °C using a multicell capillary viscometer containing pressure, temperature, and timing instrumentation. The shear rate for this test method corresponds to an apparent shear rate at the wall of 1.4 million reciprocal seconds (1.4 × 106 s−1).3 This shear rate has been found to decrease the discrepancy between this test method and other high-temperature high-shear test methods3 (Test Methods D4683 and D4741) used for engine oil specifications. Viscosities are determined directly from calibrations that have been established with Newtonian oils with nominal viscosities from 1.4 mPa·s to 5.0 mPa·s at 150 °C. The precision has only been determined for the viscosity range 1.45 mPa·s and 5.05 mPa·s at 150 °C for the materials listed in the precision section.  
1.2 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.  
1.2.1 The centiPoise (cP) is a non-SI metric unit of viscosity that is numerically equal to the milliPascal-second (mPa·s).  
1.2.2 Pounds per square inch (psi) is a non-SI unit of pressure that is approximately equal to 6.895 kPa. These units are provided for information only in 6.1.1, 7.3, 9.1.2.1, and the tables.  
1.3 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.  
1.4 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.

General Information

• Status: Published
• Publication Date: 31-Dec-2020
• ICS: 75.100 - Lubricants, industrial oils and related products
• Technical Committee: D02 - Petroleum Products, Liquid Fuels, and Lubricants
• Drafting Committee: D02.07 - Flow Properties

Relations

• Refers: ASTM D6300-24 - Standard Practice for Determination of Precision and Bias Data for Use in Test Methods for Petroleum Products, Liquid Fuels, and Lubricants
• Effective Date: 01-Mar-2024
• Refers: ASTM D6708-24 - Standard Practice for Statistical Assessment and Improvement of Expected Agreement Between Two Test Methods that Purport to Measure the Same Property of a Material
• Effective Date: 01-Mar-2024
• Refers: ASTM D6300-23a - Standard Practice for Determination of Precision and Bias Data for Use in Test Methods for Petroleum Products, Liquid Fuels, and Lubricants
• Effective Date: 01-Dec-2023
• Refers: ASTM D4683-20 - Standard Test Method for Measuring Viscosity of New and Used Engine Oils at High Shear Rate and High Temperature by Tapered Bearing Simulator Viscometer at 150 °C
• Effective Date: 01-Jun-2020
• Refers: ASTM D6300-19a - Standard Practice for Determination of Precision and Bias Data for Use in Test Methods for Petroleum Products and Lubricants
• Effective Date: 01-Dec-2019
• Refers: ASTM D6708-19 - Standard Practice for Statistical Assessment and Improvement of Expected Agreement Between Two Test Methods that Purport to Measure the Same Property of a Material
• Effective Date: 01-May-2019
• Refers: ASTM D6708-18 - Standard Practice for Statistical Assessment and Improvement of Expected Agreement Between Two Test Methods that Purport to Measure the Same Property of a Material
• Effective Date: 01-Apr-2018
• Refers: ASTM D4741-17 - Standard Test Method for Measuring Viscosity at High Temperature and High Shear Rate by Tapered-Plug Viscometer
• Effective Date: 01-Jan-2017
• Refers: ASTM D6708-16a - Standard Practice for Statistical Assessment and Improvement of Expected Agreement Between Two Test Methods that Purport to Measure the Same Property of a Material
• Effective Date: 01-Apr-2016
• Refers: ASTM D6300-16 - Standard Practice for Determination of Precision and Bias Data for Use in Test Methods for Petroleum Products and Lubricants
• Effective Date: 01-Apr-2016
• Refers: ASTM D6708-16 - Standard Practice for Statistical Assessment and Improvement of Expected Agreement Between Two Test Methods that Purport to Measure the Same Property of a Material
• Effective Date: 01-Jan-2016
• Refers: ASTM D6708-15 - Standard Practice for Statistical Assessment and Improvement of Expected Agreement Between Two Test Methods that Purport to Measure the Same Property of a Material
• Effective Date: 01-Jul-2015
• Refers: ASTM D6300-15 - Standard Practice for Determination of Precision and Bias Data for Use in Test Methods for Petroleum Products and Lubricants
• Effective Date: 01-Jun-2015
• Refers: ASTM D6300-14ae1 - Standard Practice for Determination of Precision and Bias Data for Use in Test Methods for Petroleum Products and Lubricants
• Effective Date: 01-Jun-2014
• Refers: ASTM D6300-14a - Standard Practice for Determination of Precision and Bias Data for Use in Test Methods for Petroleum Products and Lubricants
• Effective Date: 01-Jun-2014

Overview

ASTM D5481-21 is an international standard developed by ASTM International that specifies a laboratory test method for determining the high-temperature high-shear (HTHS) apparent viscosity of engine oils. This procedure uses a multicell capillary viscometer, operating at 150 °C and a high shear rate representative of severe engine service conditions. Measuring viscosity under these conditions is crucial for evaluating the performance and protective qualities of lubricants in automotive engines, especially under severe and high-stress operational scenarios.

This standard is maintained by ASTM Committee D02 on Petroleum Products, Liquid Fuels, and Lubricants, under Subcommittee D02.07 on Flow Properties.

Key Topics

• Significance of High-Temperature High-Shear Viscosity: Viscosity is a foundational property for fluid lubricants, directly impacting their ability to protect engine components, minimize wear, and ensure efficient operation at high temperatures and pressures.

• Non-Newtonian Lubricant Behavior: Many petroleum-based lubricants do not maintain a constant viscosity across all shear rates. This method accounts for shear-dependent viscosity changes, simulating real-world engine conditions.

• Test Conditions: The standard measures viscosity at 150 °C and an apparent shear rate of 1.4 × 10^6 s⁻¹, reflecting typical conditions found in engine bearings during severe service.

• Apparatus Requirements: The test uses a multicell capillary viscometer equipped with precision controls for temperature, pressure, and timing, calibrated using certified Newtonian oils.

• Results and Reporting: Outcome is reported as apparent viscosity in millipascal-seconds (mPa·s) at the test temperature. Ensuring measurement accuracy and calibration consistency is emphasized.

Applications

ASTM D5481-21 is critical for:

• Engine Oil Specification Compliance: Many equipment manufacturers and industry specifications mandate minimum high-temperature high-shear viscosities, making this method essential for product qualification and quality assurance.
• Lubricant Development and Evaluation: Research and development teams use this method to assess and optimize the performance of engine oils under extreme conditions.
• Benchmarking and Performance Testing: Laboratories and oil manufacturers utilize the standard to compare product formulations and guarantee reliable performance in modern engines.
• Automotive Industry Standards Compliance: Meeting or exceeding the requirements of this standard is often necessary for oils used in high-stress automotive environments, including heavy-duty and high-performance engines.

Related Standards

The following ASTM standards are closely related and often referenced in conjunction with ASTM D5481-21:

• ASTM D4683: Test Method for Measuring Viscosity of New and Used Engine Oils at High Shear Rate and High Temperature by Tapered Bearing Simulator Viscometer at 150 °C.
• ASTM D4741: Test Method for Measuring Viscosity at High Temperature and High Shear Rate by Tapered-Plug Viscometer.
• ASTM D6300: Practice for Determination of Precision and Bias Data for Use in Test Methods for Petroleum Products, Liquid Fuels, and Lubricants.
• ASTM D6708: Practice for Statistical Assessment and Improvement of Expected Agreement Between Two Test Methods That Purport to Measure the Same Property of a Material.

These documents provide alternative methods and practices for viscosity measurement, calibration, and statistical validation, offering a comprehensive framework for the analysis and comparison of engine oil flow properties.

---

By following ASTM D5481-21, laboratories and manufacturers can ensure rigorous, reproducible measurement of lubricant viscosity under conditions most relevant to modern engines. This supports engine health, efficiency, and compliance with ever-evolving lubricant specifications in the automotive industry.

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: D5481 − 21
Standard Test Method for
Measuring Apparent Viscosity at High-Temperature and
High-Shear Rate by Multicell Capillary Viscometer
This standard is issued under the fixed designation D5481; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision.Anumber in parentheses indicates the year of last reapproval.A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
INTRODUCTION
Severaldifferentconfigurationsofcapillaryviscometershavebeensuccessfullyusedformeasuring
the viscosity of engine oils at the high shear rates and high temperatures that occur in engines. This
test method covers the use of a single apparatus at a single temperature and single shear rate to
achieve greater uniformity and improved precision.
1. Scope* 1.2.2 Pounds per square inch (psi) is a non-SI unit of
pressure that is approximately equal to 6.895 kPa. These units
1.1 This test method covers the laboratory determination of
areprovidedforinformationonlyin6.1.1,7.3,9.1.2.1,andthe
high-temperaturehigh-shear(HTHS)viscosityofengineoilsat
tables.
a temperature of 150°C using a multicell capillary viscometer
1.3 This standard does not purport to address all of the
containing pressure, temperature, and timing instrumentation.
safety concerns, if any, associated with its use. It is the
The shear rate for this test method corresponds to an apparent
responsibility of the user of this standard to establish appro-
shear rate at the wall of 1.4 million reciprocal seconds
6 −1 3
priate safety, health, and environmental practices and deter-
(1.4×10 s ). This shear rate has been found to decrease the
mine the applicability of regulatory limitations prior to use.
discrepancy between this test method and other high-
temperature high-shear test methods (Test Methods D4683
1.4 This international standard was developed in accor-
and D4741) used for engine oil specifications. Viscosities are dance with internationally recognized principles on standard-
determined directly from calibrations that have been estab-
ization established in the Decision on Principles for the
lished with Newtonian oils with nominal viscosities from Development of International Standards, Guides and Recom-
1.4mPa·s to 5.0 mPa·s at 150°C. The precision has only been mendations issued by the World Trade Organization Technical
determined for the viscosity range 1.45mPa·s and 5.05 mPa·s Barriers to Trade (TBT) Committee.
at 150 °C for the materials listed in the precision section.
2. Referenced Documents
1.2 The values stated in SI units are to be regarded as
standard. No other units of measurement are included in this 2.1 ASTM Standards:
standard.
D4683Test Method for Measuring Viscosity of New and
Used Engine Oils at High Shear Rate and High Tempera-
1.2.1 ThecentiPoise(cP)isanon-SImetricunitofviscosity
ture by Tapered Bearing Simulator Viscometer at 150°C
that is numerically equal to the milliPascal-second (mPa·s).
D4741Test Method for Measuring Viscosity at High Tem-
peratureandHighShearRatebyTapered-PlugViscometer
D6300Practice for Determination of Precision and Bias
This test method is under the jurisdiction of ASTM Committee D02 on
Data for Use in Test Methods for Petroleum Products,
Petroleum Products, Liquid Fuels, and Lubricants and is the direct responsibility of
Liquid Fuels, and Lubricants
Subcommittee D02.07 on Flow Properties.
Current edition approved Jan. 1, 2021. Published January 2021. Originally
D6708Practice for StatisticalAssessment and Improvement
approved in 1993. Last previous edition approved in 2020 as D5481–20a. DOI:
of Expected Agreement Between Two Test Methods that
10.1520/D5481-21.
Purport to Measure the Same Property of a Material
Manning, R. E., and Lloyd, W. A., “Multicell High Temperature High-Shear
Capillary Viscometer,” SAE Paper 861562. Available from Society of Automotive
Engineers (SAE), 400 Commonwealth Dr., Warrendale, PA15096-0001, www.sae-
.org.
3 4
Girshick, F., “Non-Newtonian Fluid Dynamics in High Temperature High For referenced ASTM standards, visit the ASTM website, www.astm.org, or
Shear Capillary Viscometers,” SAE Paper 922288. Available from Society of contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM
Automotive Engineers (SAE), 400 Commonwealth Dr., Warrendale, PA 15096- Standards volume information, refer to the standard’s Document Summary page on
0001, www.sae.org. 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
D5481 − 21
3. Terminology
L = capillary length (in units consistent with R).
3.1 Definitions:
3.1.8 viscosity, n—ratio of applied shear stress and the
3.1.1 apparent viscosity, n—viscosity of a non-Newtonian
resulting rate of shear.
liquid determined by this test method at a particular shear rate
3.1.8.1 Discussion—It is sometimes called dynamic or ab-
and shear stress. soluteviscosity.Viscosityisameasureoftheresistancetoflow
of the liquid at a given temperature. In SI the unit of viscosity
3.1.2 density, n—mass per unit volume.
is the Pascal second (Pa·s), often conveniently expressed as
3.1.3 kinematic viscosity, n—-the ratio of the dynamic
milliPascal second (mPa·s), which has the English system
viscosity (η) to the density (ρ) of a liquid at a given tempera-
equivalent of the centiPoise (cP).
ture.
3.2 Definitions of Terms Specific to This Standard:
3.1.3.1 Discussion—Kinematic viscosity is a measure of a
3.2.1 calibration oils—those oils used for establishing the
fluid’s resistance to flow under the force of gravity. In the SI,
instrument’s reference framework of apparent viscosity versus
the unit of kinematic viscosity is the metre squared per second
pressure drop from which the apparent viscosities of the test
(m /s); for practical use, a submultiple (millimetre squared per
oils are determined.
second, mm /s) is more convenient. The centistoke (cSt) is
3.2.1.1 Discussion—Calibration oils, which are Newtonian
1mm /s and is often used.
fluids, are available commercially or can be blended by the
3.1.4 Newtonian oil, n—an oil or fluid that at a given
user.
temperature exhibits a constant viscosity at all shear rates or
3.2.2 test oil—any oil for which the apparent viscosity is to
shear stresses.
be determined by the test method.
3.1.5 non-Newtonian oil or fluid, n—an oil or liquid that
3.2.3 viscometric cell—that part of the viscometer compris-
exhibits a viscosity that varies with changing shear rate or
ing all parts which may be wet by the test sample, including
shear stress.
exit tube, working capillary, fill tube, pressure/exhaust
3.1.6 shear rate, n—velocity gradient perpendicular to the
connection, plug valve, and fill reservoir.
direction of flow.
3.1.6.1 Discussion—The velocity gradient in the Multi-Cell
4. Summary of Test Method
Capillary Viscometer varies across the capillary annulus from
4.1 The viscosity of the test oil in any of the viscometric
a maximum at the wall of the capillary to zero at the center of
cells is obtained by determining the pressure required to
thecapillaryannulus.Assumingaparabolicflowprofileacross
achieve a flow rate corresponding to an apparent shear rate at
thecapillary,theapparentshearrateatthecapillarywallcanbe
6 −1
thewallof1.4×10 s .Thecalibrationofeachcellisusedto
calculated as follows:
determine the viscosity corresponding to the measured pres-
S 54V/πR t (1)
sure.
a
where:
4.2 Each viscometric cell is calibrated by establishing the
−1
relationship between pressure and flow rate for a series of
S = apparent shear rate (at the wall, s ),
a
Newtonian oils of known viscosity.
V = volume of fluid (mm ) passed through the capillary in
time t (s), and
5. Significance and Use
R = capillary radius (mm).
5.1 Viscosity is an important property of fluid lubricants.
S is precise for Newtonian liquids which generate a
a
The viscosity of all fluids varies with temperature. Many
parabolic flow profile but may be approximate for non-
common petroleum lubricants are non-Newtonian: their vis-
Newtonian liquids that do not necessarily generate a para-
cosity also varies with shear rate. The usefulness of the
bolic flow profile.
viscosity of lubricants is greatest when the viscosity is mea-
3.1.7 shear stress, n—theforceperunitareainthedirection
sured at or near the conditions of shear rate and temperature
of the flow.
that the lubricants will experience in service.
3.1.7.1 Discussion—In a capillary viscometer, the signifi-
5.2 The conditions of shear rate and temperature of this test
cant shear stress is at the wall of the capillary.That is, the total
method are thought to be representative of those in the bearing
force acting on the area of the capillary annulus divided by the
of automotive engines in severe service.
insideareaofthecapillarythroughwhichtheliquidflows.The
shear stress at the wall does not depend on the nature of the
5.3 Many equipment manufacturers and lubricant specifica-
liquid (that is, whether the liquid is Newtonian or non-
tionsrequireaminimumhigh-temperaturehigh-shearviscosity
6 −1
Newtonian). The shear stress at the capillary wall may be
at 150°C and 10 s . The shear rate in capillary viscometers
calculated as follows:
variesacrosstheradiusofthecapillary.Theapparentshearrate
Z 5PR/2L (2)
where:
The sole source of supply known to the committee at this time is Cannon
Instrument Co., 2139 High Tech Rd., State College, PA16803. If you are aware of
Z = shear stress (Pa),
alternative suppliers, please provide this information to ASTM International
P = pressure drop (in Pa),
Headquarters.Your comments will receive careful consideration at a meeting of the
R = capillary radius, and
responsible technical committee, which you may attend.
D5481 − 21
at the wall for this test method is increased to compensate for 8. Sampling
the variable shear rate.
8.1 Arepresentative sample of test oil, free from suspended
5.4 This test was evaluated in an ASTM cooperative pro- solid material and water, is necessary to obtain valid results.
gram. When the sample is suspected to contain suspended material,
filter with about 10µm filter paper.
6. Apparatus
9. Calibration and Standardization
6.1 Multi-Cell Capillary High-Temperature High-Shear
9.1 Calibration:
(HTHS) Viscometer, consisting of several viscometer cells in
9.1.1 The volume and capillary diameter of each viscomet-
a temperature-controlled block and including means for con-
ric cell in the instrument is provided by the manufacturer, and
trolling and measuring temperature and applied pressure and
the nominal flow time, t , corresponding to an apparent shear
fortimingtheflowofapredeterminedvolumeoftestoil.Each o
6 −1
rate at the wall of 1.4×10 s is calculated by the manufac-
viscometric cell contains a precision glass capillary and means
turer using the following equation:
for adjusting the test oil volume to the predetermined value.
6 3
6.1.1 The Multi-Cell Capillary HTHS viscometer has the
t 54V/1.4*10 πR (3)
o
following typical dimensions and specifications:
where symbols are defined as in 3.1.6.
Diameter of capillary 0.15 mm
9.1.2 Using a minimum of four Newtonian calibration oils
Length of capillary 15 mm to 18 mm
Temperature control 150 °C ± 0.1 °C covering the viscosity range from 1.5mPa·s to 5 mPa·s at
Pressure range 350 kPa to 3500 kPa (~50 psi to
150°C, determine the relationship between pressure and flow
500 psi)
rate for each viscometric cell. The pressure should be adjusted
Pressure control ±1 %
Sample volume 7 mL ± 1 mL for each calibration oil such that the measured flow time is
within 62% of the nominal flow time, t . Make three
6.1.2 Thethermometerformeasuringthetemperatureofthe o
determinations for each oil in each cell. Follow the instrument
block is a preset digital resistance thermometer. The accuracy
supplier’s documentation for using the software “High Shear
of this thermometer may be checked by means of a special
Viscosity Calculator” to record these results.
thermowell and calibrated thermometer whose accuracy is
9.1.2.1 The following relationship can be used to express
60.1°C or better. See manufacturer’s recommendations for
the data:
procedure.
C t
η 5 C ·t·P 2 · 11C · 1 2 (4)
F G F S D G
i 1 3
7. Reagents and Materials
t t
o
7.1 NewtonianOils, havingnominalcertifiedviscositiesof
where:
1.5mPa·s to 7.0 mPa·s at 150°C. See Table 1.
η = intermediate viscosity, mPa·s,
i
t = flow time, s,
P = pressure, kPa, and
C,C,C = coefficients specific to each viscometric cell.
1 2 3
TABLE 1 Calibration Oils
9.1.2.2 Coefficient C is specific to the units in which
Approximate Approximate Pressure 1
A
Viscosity at 150 °C for Test Method pressure is expressed, as well as to each cell. Coefficient C
Calibration Oil
(mPa·s) psi kPa will be essentially constant over the relatively narrow range of
HT22 1.5 190 1310 shear rates and viscosities of interest in measurement of the
HT39 2.0 225 1550
high-temperature viscosity of automotive engine oil. In more
HT75 2.7 290 2000
general applications, C may not be constant for all values of
HT150 3.7 375 2590
HT240 5.0 480 3310 Reynolds Number.
B
HT390 7.0 645 4450
9.1.2.3 Intermediate viscosity equals viscosity for the cali-
A
Consult the supplier for specific values.
bration oils.
B
Consult the supplier for use in instruments with pressure limiters of 525 psi.
9.1.2.4 Use the suppliers “High ShearViscosity Calculator”
software to determine the calibration coefficients for each
viscometric cell.
9.1.2.5 Alternatively, AnnexA1 describes the procedure for
determining coefficients C , C , and C .
7.2 Non-Newtonian Reference Sample, having a certified 1 2 3
6 −1
viscosity at 150 °C and 10 s .
9.2 Stability of Viscosity Calibration—Checkthestabilityof
the calibration by running a calibration oil in the same manner
7.3 Carbon Dioxide or Nitrogen Cylinder, with reducer
asatestoilwouldberun.Thisshallbedonenolessfrequently
valve having a maximum pressure of at least 3500kPa
than before each new series o
...

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: D5481 − 20a D5481 − 21
Standard Test Method for
Measuring Apparent Viscosity at High-Temperature and
High-Shear Rate by Multicell Capillary Viscometer
This standard is issued under the fixed designation D5481; 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.
INTRODUCTION
Several different configurations of capillary viscometers have been successfully used for measuring
the viscosity of engine oils at the high shear rates and high temperatures that occur in engines. This
test method covers the use of a single apparatus at a single temperature and single shear rate to
achieve greater uniformity and improved precision.
1. Scope*
1.1 This test method covers the laboratory determination of high-temperature high-shear (HTHS) viscosity of engine oils at a
temperature of 150 °C using a multicell capillary viscometer containing pressure, temperature, and timing instrumentation. The
6 −1 3
shear rate for this test method corresponds to an apparent shear rate at the wall of 1.4 million reciprocal seconds (1.4 × 10 s ).
This shear rate has been found to decrease the discrepancy between this test method and other high-temperature high-shear test
methods (Test Methods D4683 and D4741) used for engine oil specifications. Viscosities are determined directly from calibrations
that have been established with Newtonian oils with nominal viscosities from 1.4 mPa·s to 5.0 mPa·s at 150 °C. The precision has
only been determined for the viscosity range 1.45 mPa·s and 5.05 mPa·s at 150 °C for the materials listed in the precision section.
1.2 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.
1.2.1 The centiPoise (cP) is a non-SI metric unit of viscosity that is numerically equal to the milliPascal-second (mPa·s).
1.2.2 Pounds per square inch (psi) is a non-SI unit of pressure that is approximately equal to 6.895 kPa. These units are provided
for information only in 6.1.1, 7.3, 9.1.2.1, and the tables.
1.3 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.
1.4 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 test method is under the jurisdiction of ASTM Committee D02 on Petroleum Products, Liquid Fuels, and Lubricants and is the direct responsibility of Subcommittee
D02.07 on Flow Properties.
Current edition approved Sept. 1, 2020Jan. 1, 2021. Published October 2020January 2021. Originally approved in 1993. Last previous edition approved in 2020 as
D5481 – 20.D5481 – 20a. DOI: 10.1520/D5481-20A.10.1520/D5481-21.
Manning, R. E., and Lloyd, W. A., “Multicell High Temperature High-Shear Capillary Viscometer,” SAE Paper 861562. Available from Society of Automotive Engineers
(SAE), 400 Commonwealth Dr., Warrendale, PA 15096-0001, www.sae.org.
Girshick, F., “Non-Newtonian Fluid Dynamics in High Temperature High Shear Capillary Viscometers,” SAE Paper 922288. Available from Society of Automotive
Engineers (SAE), 400 Commonwealth Dr., Warrendale, PA 15096-0001, www.sae.org.
*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
D5481 − 21
2. Referenced Documents
2.1 ASTM Standards:
D4683 Test Method for Measuring Viscosity of New and Used Engine Oils at High Shear Rate and High Temperature by Tapered
Bearing Simulator Viscometer at 150 °C
D4741 Test Method for Measuring Viscosity at High Temperature and High Shear Rate by Tapered-Plug Viscometer
D6300 Practice for Determination of Precision and Bias Data for Use in Test Methods for Petroleum Products, Liquid Fuels, and
Lubricants
D6708 Practice for Statistical Assessment and Improvement of Expected Agreement Between Two Test Methods that Purport
to Measure the Same Property of a Material
3. Terminology
3.1 Definitions:
3.1.1 apparent viscosity, n—viscosity of a non-Newtonian liquid determined by this test method at a particular shear rate and shear
stress.
3.1.2 density, n—mass per unit volume at a specified temperature.volume.
3.1.2.1 Discussion—
For common fuel and lubricant applications, density at atmospheric pressure is assumed. However, high pressure can impact
density.
3.1.3 kinematic viscosity, n—-the ratio of the dynamic viscosity (η) to the density (ρ) of a liquid at a given temperature.
3.1.3.1 Discussion—
Kinematic viscosity is a measure of a fluid’s resistance to flow under the force of gravity. In the SI, the unit of kinematic viscosity
2 2
is the metre squared per second (m /s); for practical use, a submultiple (millimetre squared per second, mm /s) is more convenient.
The centistoke (cSt) is 1 mm /s and is often used.
3.1.4 Newtonian oil, n—an oil or fluid that at a given temperature exhibits a constant viscosity at all shear rates or shear stresses.
3.1.5 non-Newtonian oil or fluid, n—an oil or liquid that exhibits a viscosity that varies with changing shear rate or shear stress.
3.1.6 shear rate, n—velocity gradient perpendicular to the direction of flow.
3.1.6.1 Discussion—
The velocity gradient in the Multi-Cell Capillary Viscometer varies across the capillary annulus from a maximum at the wall of
the capillary to zero at the center of the capillary annulus. Assuming a parabolic flow profile across the capillary, the apparent shear
rate at the capillary wall can be calculated as follows:
S 5 4V/πR t (1)
a
where:
−1
S = apparent shear rate (at the wall, s ),
a
V = volume of fluid (mm ) passed through the capillary in time t (s), and
R = capillary radius (mm).
S is precise for Newtonian liquids which generate a parabolic flow profile but may be approximate for non-Newtonian liquids
a
that do not necessarily generate a parabolic flow profile.
3.1.7 shear stress, n—the force per unit area in the direction of the flow.
3.1.7.1 Discussion—
In a capillary viscometer, the significant shear stress is at the wall of the capillary. That is, the total force acting on the area of the
capillary annulus divided by the inside area of the capillary through which the liquid flows. The shear stress at the wall does not
depend on the nature of the liquid (that is, whether the liquid is Newtonian or non-Newtonian). The shear stress at the capillary
wall may be calculated as follows:
For referenced ASTM standards, visit the ASTM website, www.astm.org, or contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM Standards
volume information, refer to the standard’s Document Summary page on the ASTM website.
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Z 5 PR/2L (2)
where:
Z = shear stress (Pa),
P = pressure drop (in Pa),
R = capillary radius, and
L = capillary length (in units consistent with R).
3.1.8 viscosity, n—ratio of applied shear stress and the resulting rate of shear.
3.1.8.1 Discussion—
It is sometimes called dynamic or absolute viscosity. Viscosity is a measure of the resistance to flow of the liquid at a given
temperature. In SI the unit of viscosity is the Pascal second (Pa·s), often conveniently expressed as milliPascal second (mPa·s),
which has the English system equivalent of the centiPoise (cP).
3.2 Definitions of Terms Specific to This Standard:
3.2.1 calibration oils—those oils used for establishing the instrument’s reference framework of apparent viscosity versus pressure
drop from which the apparent viscosities of the test oils are determined.
3.2.1.1 Discussion—
Calibration oils, which are Newtonian fluids, are available commercially or can be blended by the user.
3.2.2 test oil—any oil for which the apparent viscosity is to be determined by the test method.
3.2.3 viscometric cell—that part of the viscometer comprising all parts which may be wet by the test sample, including exit tube,
working capillary, fill tube, pressure/exhaust connection, plug valve, and fill reservoir.
4. Summary of Test Method
4.1 The viscosity of the test oil in any of the viscometric cells is obtained by determining the pressure required to achieve a flow
6 −1
rate corresponding to an apparent shear rate at the wall of 1.4 × 10 s . The calibration of each cell is used to determine the
viscosity corresponding to the measured pressure.
4.2 Each viscometric cell is calibrated by establishing the relationship between pressure and flow rate for a series of Newtonian
oils of known viscosity.
5. Significance and Use
5.1 Viscosity is an important property of fluid lubricants. The viscosity of all fluids varies with temperature. Many common
petroleum lubricants are non-Newtonian: their viscosity also varies with shear rate. The usefulness of the viscosity of lubricants
is greatest when the viscosity is measured at or near the conditions of shear rate and temperature that the lubricants will experience
in service.
5.2 The conditions of shear rate and temperature of this test method are thought to be representative of those in the bearing of
automotive engines in severe service.
5.3 Many equipment manufacturers and lubricant specifications require a minimum high-temperature high-shear viscosity at
6 −1
150 °C and 10 s . The shear rate in capillary viscometers varies across the radius of the capillary. The apparent shear rate at the
wall for this test method is increased to compensate for the variable shear rate.
5.4 This test was evaluated in an ASTM cooperative program.
The sole source of supply known to the committee at this time is Cannon Instrument Co., 2139 High Tech Rd., State College, PA 16803. If you are aware of alternative
suppliers, please provide this information to ASTM International Headquarters. Your comments will receive careful consideration at a meeting of the responsible technical
committee, which you may attend.
Supporting data have been filed at ASTM International Headquarters and may be obtained by requesting Research Report RR:D02-1767. Contact ASTM Customer
Service at [e-mail].
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6. Apparatus
6.1 Multi-Cell Capillary High-Temperature High-Shear (HTHS) Viscometer, consisting consisting of several viscometer cells in
a temperature-controlled block and including means for controlling and measuring temperature and applied pressure and for timing
the flow of a predetermined volume of test oil. Each viscometric cell contains a precision glass capillary and means for adjusting
the test oil volume to the predetermined value.
6.1.1 The Multi-Cell Capillary HTHS viscometer has the following typical dimensions and specifications:
Diameter of capillary 0.15 mm
Length of capillary 15 mm to 18 mm
Temperature control 150 °C ± 0.1 °C
Pressure range 350 kPa to 3500 kPa (~50 psi to
500 psi)
Pressure control ±1 %
Sample volume 7 mL ± 1 mL
6.1.2 The thermometer for measuring the temperature of the block is a preset digital resistance thermometer. The accuracy of this
thermometer may be checked by means of a special thermowell and calibrated thermometer whose accuracy is 60.1 °C or better.
See manufacturer’s recommendations for procedure.
7. Reagents and Materials
7.1 Newtonian Oils, having nominal certified viscosities of 1.5 mPa·s to 7.0 mPa·s at 150 °C. See Table 1.
TABLE 1 Calibration Oils
Approximate Approximate Pressure
A
Viscosity at 150 °C for Test Method
Calibration Oil
(mPa·s) psi kPa
HT22 1.5 190 1310
HT39 2.0 225 1550
HT75 2.7 290 2000
HT150 3.7 375 2590
HT240 5.0 480 3310
B
HT390 7.0 645 4450
A
Consult the supplier for specific values.
B
Consult the supplier for use in instruments with pressure limiters of 525 psi.
5 6 −1
7.2 Non-Newtonian Reference Sample, having a certified viscosity at 150 °C and 10 s .
7.3 Carbon Dioxide or Nitrogen Cylinder, with reducer valve having a maximum pressure of at least 3500 kPa (~500 psi).
8. Sampling
8.1 A representative sample of test oil, free from suspended solid material and water, is necessary to obtain valid results. When
the sample is suspected to contain suspended material, filter with about 10 μm filter paper.
9. Calibration and Standardization
9.1 Calibration:
9.1.1 The volume and capillary diameter of each viscometric cell in the instrument is provided by the manufacturer, and the
6 −1
nominal flow time, t , corresponding to an apparent shear rate at the wall of 1.4 × 10 s is calculated by the manufacturer using
o
the following equation:
6 3
t 5 4V/1.4*10 πR (3)
o
where symbols are defined as in 3.1.6.
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9.1.2 Using a minimum of four Newtonian calibration oils covering the viscosity range from 1.5 mPa·s to 5 mPa·s at 150 °C,
determine the relationship between pressure and flow rate for each viscometric cell. The pressure should be adjusted for each
calibration oil such that the measured flow time is within 62 % of the nominal flow time, t . Make three determinations for each
o
oil in each cell. Follow the instrument supplier’s documentation for using the software “High Shear Viscosity Calculator” to record
these results.
9.1.2.1 The following relationship can be used to express the data:
C t
η 5 C ·t·P 2 · 11C · 12 (4)
F G F S D G
i 1 3
t t
o
where:
η = intermediate viscosity, mPa·s,
i
t = flow time, s,
P = pressure, kPa, and
C , C , C = coefficients specific to each viscometric cell.
1 2 3
9.1.2.2 Coefficient C is specific to the units in which pressure is expressed, as well as to each cell. Coefficient C will be
1 2
essentially constant over the relatively narrow range of shear rates and viscosities of interest in measurement of the
high-temperature viscosity of automotive engine oil. In more general applications, C may not be constant for all values of
Reynolds Number.
9.1.2.3 Intermediate viscosity equals viscosity for the calibration oils.
9.1.2.4 Use the suppliers “High Shear Viscosity Calculator” software to determine the calibration coefficients for eac
...