ASTM D3829-20a

Standard Test Method for Predicting the Borderline Pumping Temperature of Engine Oil

SIGNIFICANCE AND USE
5.1 Borderline pumping temperature is a measure of the lowest temperature at which an engine oil can be continuously and adequately supplied to the oil pump inlet of an automotive engine.
SCOPE
1.1 This test method covers the prediction of the borderline pumping temperature (BPT) of engine oils through the use of a 16 h cooling cycle over the temperature range from 0 °C to −40 °C. The precision is stated for temperatures from –34 °C to –15 °C.  
1.2 Applicability to petroleum products other than engine oils has not been determined.  
1.3 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.  
1.3.1 Exception—This test method uses the SI based unit of milliPascal second (mPa·s) for viscosity, which is equivalent to centipoise (cP).  
1.4 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.  
1.5 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-Oct-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 E563-11 - Standard Practice for Preparation and Use of an Ice-Point Bath as a Reference Temperature
• Effective Date: 01-May-2011
• Refers: ASTM E563-08 - Standard Practice for Preparation and Use of an Ice-Point Bath as a Reference Temperature
• Effective Date: 01-Nov-2008
• Refers: ASTM E563-02e1 - Standard Practice for Preparation and Use of an Ice-Point Bath as a Reference Temperature
• Effective Date: 10-Oct-2002
• Refers: ASTM E563-02 - Standard Practice for Preparation and Use of an Ice-Point Bath as a Reference Temperature
• Effective Date: 10-Oct-2002

Overview

ASTM D3829-20a is the industry-recognized standard test method for predicting the borderline pumping temperature (BPT) of engine oils. Developed by ASTM International, this method assesses the lowest temperature at which engine oil can be continuously and adequately delivered to the oil pump inlet in automotive engines. Using a controlled 16-hour cooling cycle across a temperature range of 0 °C to −40 °C, the method helps ensure reliable engine performance, particularly in cold climates. The results enable manufacturers and laboratories to benchmark the low-temperature flow properties of lubricants, thereby supporting safe and effective engine operations.

Key Topics

• Borderline Pumping Temperature (BPT): Defined as the maximum temperature at which either critical yield stress or critical viscosity occurs, this is a key indicator of engine oil performance in low-temperature conditions.
• Cooling Cycle: The method prescribes a 16-hour cooling period, including a nonlinear cooling rate from 80 °C to the test temperature, to simulate real-world cold start conditions.
• Measurement and Apparatus: Testing involves a mini-rotary viscometer and calibrated temperature measuring devices, such as digital contact thermometers or liquid-in-glass thermometers, to assess viscosity and yield stress.
• Calibration and Standardization: Ensuring precise measurements requires regular calibration of instruments, the use of certified reference oils, and adherence to ISO and ASTM calibration standards.
• Precision and Reproducibility: The method offers repeatability within 1.3 °C and reproducibility within 3.2 °C across different laboratories, ensuring robust, comparable results.
• Health, Safety, and Environment: Users are responsible for implementing appropriate safety, health, and environmental practices when conducting the test.

Applications

The ASTM D3829-20a method is crucial for:

• Engine Oil Development: Facilitates the design and formulation of lubricants with reliable low-temperature pumpability, which is essential for vehicle operation in colder climates.
• Quality Control: Routine laboratory testing of engine oils to verify that products meet industry specifications for low-temperature performance.
• Specification Compliance: Assists manufacturers in demonstrating conformity with industry and OEM (original equipment manufacturer) requirements for low-temperature oil flow.
• Comparative Evaluation: Provides objective data for comparing different engine oil formulations and identifying potential improvements related to viscosity and flow characteristics.
• Research and Development: Enables laboratories and R&D teams to study the relationship between oil composition, viscosity, and cold flow properties.

Related Standards

For comprehensive evaluation and compatibility, consider these relevant ASTM and ISO standards:

• ASTM D8278: Specification for digital contact thermometers used in fuel and lubricant testing.
• ASTM E563: Practice for preparation and use of an ice-point bath as a reference temperature.
• ASTM E644: Test methods for industrial resistance thermometers.
• ASTM E1137: Specification for industrial platinum resistance thermometers.
• ASTM E2877: Guide for digital contact thermometers.
• ISO 17025: General requirements for the competence of testing and calibration laboratories.
• ISO Guide 34: General requirements for the competence of reference material producers.

By following ASTM D3829-20a, organizations can ensure more reliable engine oil performance in cold weather, reducing maintenance risks and promoting engine longevity. This standard supports the global petroleum and automotive industries in providing products that meet demanding environmental and operational requirements.

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: D3829 − 20a
Standard Test Method for
Predicting the Borderline Pumping Temperature of Engine
Oil
This standard is issued under the fixed designation D3829; 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.
1. Scope* 2.2 ISO Standards:
ISO 17025General requirements for the competence of
1.1 This test method covers the prediction of the borderline
testing and calibration laboratories
pumping temperature (BPT) of engine oils through the use of
ISO Guide 34General requirements for the competence of
a 16h cooling cycle over the temperature range from 0°C to
reference material producers
−40°C.Theprecisionisstatedfortemperaturesfrom–34°Cto
–15°C.
3. Terminology
1.2 Applicability to petroleum products other than engine
3.1 Definitions:
oils has not been determined.
3.1.1 apparent viscosity, n—the determined viscosity ob-
tained by use of this test method.
1.3 The values stated in SI units are to be regarded as
3.1.2 digital contact thermometer (DCT), n—an electronic
standard. No other units of measurement are included in this
standard. device consisting of a digital display and associated tempera-
ture sensing probe.
1.3.1 Exception—This test method uses the SI based unit of
3.1.2.1 Discussion—This device consists of a temperature
milliPascalsecond(mPa·s)forviscosity,whichisequivalentto
sensor connected to a measuring instrument; this instrument
centipoise (cP).
measures the temperature-dependent quantity of the sensor,
1.4 This standard does not purport to address all of the
computes the temperature from the measured quantity, and
safety concerns, if any, associated with its use. It is the
provides a digital output. This digital output goes to a digital
responsibility of the user of this standard to establish appro-
displayand/orrecordingdevicethatmaybeinternalorexternal
priate safety, health, and environmental practices and deter-
to the device.
mine the applicability of regulatory limitations prior to use.
3.1.2.2 Discussion—The devices are often referred to as a
1.5 This international standard was developed in accor-
“digitalthermometers,”howeverthetermincludesdevicesthat
dance with internationally recognized principles on standard-
sense temperature by means other than being in physical
ization established in the Decision on Principles for the
contact with the media.
Development of International Standards, Guides and Recom-
3.1.2.3 Discussion—PET is an acronym for portable elec-
mendations issued by the World Trade Organization Technical
tronic thermometers, a subset of digital contact thermometers
Barriers to Trade (TBT) Committee.
(DCT).
3.1.3 Newtonian oil or fluid, n—anoilorfluidthatatagiven
2. Referenced Documents
temperature exhibits a constant viscosity at all shear rates or
2.1 ASTM Standards: shear stresses.
D8278Specification for Digital Contact Thermometers for
3.1.4 non-Newtonian oil or fluid, n—an oil or fluid that at a
Test Methods Measuring Flow Properties of Fuels and
given temperature exhibits a viscosity that varies with chang-
Lubricants
ing shear stress or shear rate.
E563Practice for Preparation and Use of an Ice-Point Bath
3.1.5 viscosity, n—the ratio between the applied shear stress
as a Reference Temperature
and rate of shear which is sometimes called the coefficient of
dynamic viscosity and is a measure of the resistance to flow of
the liquid.
This test method is under the jurisdiction of ASTM Committee D02 on
3.2 Definitions of Terms Specific to This Standard:
Petroleum Products, Liquid Fuels, and Lubricants and is the direct responsibility of
Subcommittee D02.07 on Flow Properties.
Current edition approved Nov. 1, 2020. Published November 2020. Originally
approved in 1979. Last previous edition approved in 2020 as D3829–20. DOI: Available fromAmerican National Standards Institute (ANSI), 25 W. 43rd St.,
10.1520/D3829-20A. 4th Floor, New York, NY 10036, http://www.ansi.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
D3829 − 20a
3.2.1 borderline pumping temperature, n—the maximum T 5 31.7M 310 (6)
r
temperature at which the critical yield stress or critical viscos-
τ 5 3.5M (7)
ity occurs, whichever is the higher temperature.
3.2.7 test oil, n—any oil for which the apparent viscosity
3.2.2 calibration oils, n—those oils for establishing the
and yield stress are to be determined by use of the test method
instrument’s reference framework of apparent viscosity versus
under description.
speed from which the apparent viscosities of test oils are
3.2.8 yield stress, n—the shear stress required to initiate
determined.
flow.
3.2.3 critical viscosity, n—the maximum viscosity at a
3.2.8.1 Discussion—For all Newtonian fluids and some
defined shear rate to allow adequate flow of oil to the oil pump
non-Newtonian fluids, yield stress is zero. An oil can have a
inanautomotiveengine.Ahigherviscositycancausefailureto
yield stress that is a function of its low-temperature cooling
maintain adequate oil pressure through the limiting of flow
rate, soak time, and temperature.
through the oil screen or oil inlet tubes.
3.2.4 critical yield stress, n—the maximum yield stress that
4. Summary of Test Method
allows oil to flow to the inlet oil screen in an automotive
4.1 Anengineoilsampleiscooledfrom80°Ctothedesired
engine. With a higher yield stress, air may be drawn into the
testtemperatureatanonlinearprogrammedcoolingrateovera
pump and cause failure to maintain adequate oil pressure
10 h period and held at the test temperature for the remainder
through air-binding of the pump.
of a 16h period. After completion of the soak period, two
3.2.5 shear rate, n—the velocity gradient in fluid flow.
standard torques of increasing severity are applied to the rotor
shaft and the speed of rotation in each case is measured. From
3.2.5.1 Discussion—For a Newtonian fluid in a concentric
the results at three or more temperatures, the borderline
cylinder rotary viscometer in which the shear stress is mea-
pumping temperature is determined.
sured at the inner cylinder surface (such as the apparatus
describedin6.1),andignoringanyendeffects,theshearrateis
4.2 Alternatively, for some specification or classification
given as follows:
purposes it may be sufficient to determine that the BPT is less
than a certain specified temperature.
2ΩR
s
γ˙ 5 (1)
2 2
~R 2 R !
s r
5. Significance and Use
4πR
s
γ˙ 5 (2)
2 2 5.1 Borderline pumping temperature is a measure of the
t R 2 R
~ !
s r
lowest temperature at which an engine oil can be continuously
where:
and adequately supplied to the oil pump inlet of an automotive
γ˙ = shear rate at the surface of the rotor in reciprocal engine.
−1
seconds, s ,
6. Apparatus
Ω = angular velocity, rad/s,
R = stator radius, mm, 3
s
6.1 Mini-Rotary Viscometer, consisting of one or more
R = rotor radius, mm, and
r
viscometric cells including a calibrated rotor-stator assembly,
t = time in seconds for one revolution of the rotor.
which are contained in a temperature-controlled aluminum
For the specific apparatus being described in 6.1.1,
block.
6.1.1 The viscometric cell has the following nominal di-
γ˙ 5 (3)
mensions:
t
Diameter of rotor 17.06 mm ± 0.08 mm
3.2.6 shear stress, n—the motivating force per unit area for
Length of rotor 20.00 mm ± 0.14 mm
Inside of diameter of cup 19.07 mm ± 0.08 mm
fluid flow.
Radius of shaft 3.18 mm ± 0.13 mm
Radius of string 0.1 mm
3.2.6.1 Discussion—For the rotary viscometer being de-
scribed in 6.1, the rotor surface is the area under shear or the
6.2 Weights:
shear area. For this test method, end effects are not considered. 6.2.1 Yield Stress Measurement—A set of nine disks and a
26 disk holder, each with a mass of 10 g 6 0.1 g.
T 5 9.81M~R 1R ! 310 (4)
r o t
6.2.2 Viscosity Measurement—Weightwithmassof150g 6
T
r
1.0 g.
τ 5 310 (5)
2π R h
r
6.3 Temperature Measuring Device—Use either a DCT
where:
meeting the requirements described in 6.3.1 or liquid-in-glass
T = torque applied to rotor, N·m,
thermometers as described in 6.3.2. A calibrated DCT or
r
M = applied mass, g,
R = radius of the shaft, mm,
o
R = radius of the thread, mm, The sole source of supply of the apparatus known to the committee at this time
t
is Cannon Instrument Co., P.O. Box 16, State College, PA16801. If you are aware
τ = shear stress at the rotor surface, Pa, and
of alternative suppliers, please provide this information to ASTM International
h = height of the rotor, mm.
Headquarters.Your comments will receive careful consideration at a meeting of the
For the dimensions given in 6.1.1, responsible technical committee, which you may attend.
D3829 − 20a
calibrated low temperature liquid-in-glass thermometer shall 6.4 Temperature Control System—Regulatesthemini-rotary
be used as the thermometer for temperature measurement viscometer block temperature in accordance with the tempera-
below 25°C independent of the instrument’s temperature ture requirements described in Table X1.1.
control, and shall be located in the thermowell.
6.5 Cell Cap—A cover inserted into the top of the viscom-
eter cell to minimize room air circulation into the cells is
NOTE 1—The display device and sensor must be correctly paired.
required for thermoelectrically cooled instruments. The cell
Incorrect pairing will result in temperature measurement errors and
possibly irreversible damage to the electronics of the display.
cap is a stepped cylinder 38mm 6 1 mm in length made of a
low thermal conductivity material, for example, thermoplastic
6.3.1 Digital Contact Thermometer—Use D02-DCT14
such as acetyl copolymers that have known solvent resistivity
listed in Specification D8278. As an alternative to the 3mm
and are suitable for use between the temperature ranges of this
metal sheathed probe noted in Specification D8278, a glass
testmethod.Thetophalfis28mm 61mmindiameterandthe
sheathed DCT probe with a 6mm O.D. is acceptable provided
bottom half is 19 mm in diameter with a tolerance consistent
it meets the other requirements shown for D02-DCT14 in
withthecelldiameter.Thetoleranceonthebottomhalfissuch
Specification D8278. A DCT display resolution of 0.01C is
thatitwilleasilyfitintocellbutnotallowthecaptocontactthe
preferable. If thermowell ID is larger than the probe OD, then
rotorshaft.Thepiecehasacenterboreof11mm 61mm.The
ametallicsleevemustbeusedtofillthegapbetweentheprobe
cap is made in two halves to facilitate placement in the top of
OD and thermowell ID with a length of 58mm.
the cell.
6.3.1.1 The DCT calibration drift shall be checked at least
6.5.1 Cell caps shall not be used in the direct refrigeration
annually by either measuring the ice point or against a
instruments, since such use would block the flow of cold, dry
reference thermometer in a constant temperature bath at the
air into the stators to keep them frost-free.
prescribed immersion depth to ensure compliance with 6.3.1.
6.6 Supply of Dry Gas—A supply of dry filtered dry gas to
With respect to an ice bath, Practice E563 provides guidance
minimize moisture condensation on the upper portions of the
onthepreparationanduseofanicebath.However,forthisuse,
instrument.
variance from the specific steps, such as water source, is
6.6.1 For thermoelectric cooled instruments, which use cell
permitted provided preparation is consistent. The basis for the
caps,thedrygassupplyisconnectedtothehousingcover.The
variance is due to the reference being used to track change in
supply of dry gas is discontinued when the cover is removed
calibration not verification.
for the measurement phase of the test.
NOTE 2—When a DCT’s calibration drifts in one direction over several
6.7 Locking Pin—A device to keep the rotor from turning
calibration checks, that is, ice point, it may be an indication of deteriora-
tion of the DCT. prematurely and able to stop the rotor at the nearest half
revolution by interaction with the rotor crossbar.
6.3.2 For liquid-in-glass, LiG, thermometers, two are re-
quired.OneLiGshallbeacalibrated76mmpartialimmersion
7. Reagents and Materials
thermometer with a scale from +5°C to 1 degree less than the
7.1 Low Cloud-Point, Newtonian Oil, a calibration oil of
lowest test temperature in 0.2°C subdivisions. This low
approximately30Pa·sviscosityat−20°Cforcalibrationofthe
temperatureLiGthermometershallhaveareportofcalibration
viscometric cells. The calibration oil shall be obtained from
showing the temperature deviation at each calibrated test
suppliers complying with ISO Guide 34 and ISO 17025 with
temperature. The second LiG thermometer shall be a 76 mm
traceability to a national metrology institute (NMI).
partial immersion thermometer graduated from at least +70°C
to 90°C in 1°C subdivisions, which is used to verify the
7.2 Methanol, commercial or technical grade of dry metha-
preheat temperature.
nol is suitable for the cooling bath.
6.3.2.1 Calibration Check—Verify the low temperature
7.3 Oil Solvent, commercial heptanes or similar solvent is
thermometer at least annually against a reference thermometer
suitable.
in a constant temperature bath or an ice bath.The thermometer
7.4 Acetone, technical grade of acetone is suitable provided
istobeinsertedtoitsimmersiondepth.Ifusinganicebath,the
it does not leave a residue upon evaporation.
ice point reading is to be taken within 60 min after the
thermometer has been at test temperature for at least 3 min. If
8. Sampling
the corrected temperature reading deviates from the reference
8.1 Arepresentative sample of test oil free from suspended
thermometer or the ice point then repeat this calibration check.
solid material and water is necessary to obtain valid results. If
If the thermometer deviates from the reference value on two
the sample in its container is received below the dew-point
successive checks then a full thermometer recalibration is
temperature of the room, allow to warm to room temperature
needed.
before opening.
6.3.2.2 Recalibration—A complete recalibration of the
liquid-in-glass thermometer, while permitted, is not necessary
9. Calibration and Standardization
in order to meet the accuracy ascribed to liquid-in-glass
thermometer’s design until the thermometers corrected mea- 9.1 Temperature Control Calibration Procedure—Calibrate
sured temperature deviates from the reference thermometer or the MRV temperature control by comparing the instruments
ice point by one scale division, or until five years has elapsed displayed temperature against a thermometer in the thermow-
since the last full calibration. ell. The thermometer used shall meet the requirements in 6.3.
D3829 − 20a
9.1.1 Place 10 mL of a typical test fluid and rotor in each C 5η ⁄t (8)
cell.Ifrequired,placecellcapsovereachcellthenplacecover
where:
on instrument. Cell caps shall not be used on direct refrigera-
η = viscosity of the standard oil, mPa·s at –20°C,
tion instruments (see 6.5.1).
C = cell constant for an applied mass of 150 g, mPa, and
9.1.2 Place the thermometer in the thermowell. See Note 3.
t = time in seconds for three revolutions.
Thisthermowellistobeusedforalltemperaturemeasurements
9.10 If corrected values for the instrument’s temperature
below 25°C.
control and thermometer deviate by more than the tolerance
NOTE 3—Prior to inserting the thermometer or DCT probe in the
(60.1°C), use the procedure in X2.1 to assist in determining
thermowell, place several drops (~3) of a heat transfer fluid such as 50/50
the cause and correction.
water/ethylene glycol mix, CCS reference oil CL100 or a dewaxed low
viscosity mineral oil in the thermowell.
10. Yield Stress and Viscosity Measurement Procedure
9.1.3 Make the temperature measurements at 80°C then at
least three measurements that are 5°C apart from –5°C to the 10.1 Viscometric Cell Preparation:
lowest test temperature used including both end points to
10.1.1 If the cells are not clean, clean according to 10.7
establish a calibration curve for this combination of thermom-
cleaning procedure.
eter and the instrument’s temperature control. Make at least
10.1.2 Place 10mL 6 0.2 mLof test oil sample into a clean
two temperature measurements at every calibration tempera-
cell.
ture with at least 10 min between observations.
10.1.2.1 All cells should contain a fluid and rotor; if there
arelessthanafullsetofsamplestorun,filleachoftheunused
NOTE 4—All temperatures in this test method refer to the actual
cells with 10 mL of a typical test sample.
temperature and not necessarily the indicated temperature.
10.1.3 Repeat 10.1.2 until all test samples are in their cells.
9.1.4 Follow the instrument manufacturers instructions for
10.1.4 Place each rotor in its cell, and place upper pivot pin
correcting the instrument’s measured temperature.
in position, including those for any unused cells.
Alternatively, establish a correction equation between ther-
mometer and instrument’s measured temperature then adjust
NOTE5—Beforeinsertingtherotorsinthecells,inspecteachrotortobe
surethattheshaftisstraight,thattherotorsurfaceissmoothandfreefrom
each temperature of the cooling program by the offset deter-
dents, scratches, and other imperfections. For rotors with a bearing point
mine
...

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: D3829 − 20 D3829 − 20a
Standard Test Method for
Predicting the Borderline Pumping Temperature of Engine
Oil
This standard is issued under the fixed designation D3829; 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 test method covers the prediction of the borderline pumping temperature (BPT) of engine oils through the use of a 16 h
cooling cycle over the temperature range from 0 °C to −40 °C. The precision is stated for temperatures from –34 °C to –15 °C.
1.2 Applicability to petroleum products other than engine oils has not been determined.
1.3 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.
1.3.1 Exception—This test method uses the SI based unit of milliPascal second (mPa·s) for viscosity, which is equivalent to
centipoise (cP).
1.4 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.
1.5 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.
2. Referenced Documents
2.1 ASTM Standards:
D8278 Specification for Digital Contact Thermometers for Test Methods Measuring Flow Properties of Fuels and Lubricants
E563 Practice for Preparation and Use of an Ice-Point Bath as a Reference Temperature
E644 Test Methods for Testing Industrial Resistance Thermometers
E1137 Specification for Industrial Platinum Resistance Thermometers
E2877 Guide for Digital Contact Thermometers
2.2 ISO Standards:
ISO 17025 General requirements for the competence of testing and calibration laboratories
ISO Guide 34 General requirements for the competence of reference material producers
3. Terminology
3.1 Definitions:
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 June 1, 2020Nov. 1, 2020. Published June 2020November 2020. Originally approved in 1979. Last previous edition approved in 20182020 as
D3829 – 18.D3829 – 20. DOI: 10.1520/D3829-20.10.1520/D3829-20A.
Available from American National Standards Institute (ANSI), 25 W. 43rd St., 4th Floor, New York, NY 10036, http://www.ansi.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
D3829 − 20a
3.1.1 apparent viscosity, n—the determined viscosity obtained by use of this test method.
3.1.2 digital contact thermometer (DCT), n—an electronic device consisting of a digital display and associated temperature
sensing probe.
3.1.2.1 Discussion—
This device consists of a temperature sensor connected to a measuring instrument; this instrument measures the temperature-
dependent quantity of the sensor, computes the temperature from the measured quantity, and provides a digital output. This digital
output goes to a digital display and/or recording device that may be internal or external to the device. These devices are sometimes
referred to as “digital thermometers.”
3.1.2.2 Discussion—
The devices are often referred to as a “digital thermometers,” however the term includes devices that sense temperature by means
other than being in physical contact with the media.
3.1.2.3 Discussion—
PET is an acronym for portable electronic thermometers, a subset of digital contact thermometers (DCT).
3.1.3 Newtonian oil or fluid, n—an oil or fluid that at a given temperature exhibits a constant viscosity at all shear rates or shear
stresses.
3.1.4 non-Newtonian oil or fluid, n—an oil or fluid that at a given temperature exhibits a viscosity that varies with changing shear
stress or shear rate.
3.1.5 viscosity, n—the ratio between the applied shear stress and rate of shear which is sometimes called the coefficient of dynamic
viscosity and is a measure of the resistance to flow of the liquid.
3.2 Definitions of Terms Specific to This Standard:
3.2.1 borderline pumping temperature, n—the maximum temperature at which the critical yield stress or critical viscosity occurs,
whichever is the higher temperature.
3.2.2 calibration oils, n—those oils for establishing the instrument’s reference framework of apparent viscosity versus speed from
which the apparent viscosities of test oils are determined.
3.2.3 critical viscosity, n—the maximum viscosity at a defined shear rate to allow adequate flow of oil to the oil pump in an
automotive engine. A higher viscosity can cause failure to maintain adequate oil pressure through the limiting of flow through the
oil screen or oil inlet tubes.
3.2.4 critical yield stress, n—the maximum yield stress that allows oil to flow to the inlet oil screen in an automotive engine. With
a higher yield stress, air may be drawn into the pump and cause failure to maintain adequate oil pressure through air-binding of
the pump.
3.2.5 shear rate, n—the velocity gradient in fluid flow.
3.2.5.1 Discussion—
For a Newtonian fluid in a concentric cylinder rotary viscometer in which the shear stress is measured at the inner cylinder surface
(such as the apparatus described in 6.1), and ignoring any end effects, the shear rate is given as follows:
2ΩR
s
γ˙ 5 (1)
2 2
~R 2 R !
s r
4πR
s
γ˙ 5 (2)
2 2
t R 2 R
~ !
s r
where:
−1
γ˙ = shear rate at the surface of the rotor in reciprocal seconds, s ,
Ω = angular velocity, rad/s,
R = stator radius, mm,
s
R = rotor radius, mm, and
r
D3829 − 20a
t = time in seconds for one revolution of the rotor.
For the specific apparatus being described in 6.1.1,
γ˙ 5 (3)
t
3.2.6 shear stress, n—the motivating force per unit area for fluid flow.
3.2.6.1 Discussion—
For the rotary viscometer being described in 6.1, the rotor surface is the area under shear or the shear area. For this test method,
end effects are not considered.
T 5 9.81M R 1R 310 (4)
~ !
r o t
T
r
τ 5 310 (5)
2π R h
r
where:
T = torque applied to rotor, N·m,
r
M = applied mass, g,
R = radius of the shaft, mm,
o
R = radius of the thread, mm,
t
τ = shear stress at the rotor surface, Pa, and
h = height of the rotor, mm.
For the dimensions given in 6.1.1,
T 5 31.7M 310 (6)
r
τ 5 3.5M (7)
3.2.7 test oil, n—any oil for which the apparent viscosity and yield stress are to be determined by use of the test method under
description.
3.2.8 yield stress, n—the shear stress required to initiate flow.
3.2.8.1 Discussion—
For all Newtonian fluids and some non-Newtonian fluids, yield stress is zero. An oil can have a yield stress that is a function of
its low-temperature cooling rate, soak time, and temperature.
4. Summary of Test Method
4.1 An engine oil sample is cooled from 80 °C to the desired test temperature at a nonlinear programmed cooling rate over a 10
h period and held at the test temperature for the remainder of a 16 h period. After completion of the soak period, two standard
torques of increasing severity are applied to the rotor shaft and the speed of rotation in each case is measured. From the results
at three or more temperatures, the borderline pumping temperature is determined.
4.2 Alternatively, for some specification or classification purposes it may be sufficient to determine that the BPT is less than a
certain specified temperature.
5. Significance and Use
5.1 Borderline pumping temperature is a measure of the lowest temperature at which an engine oil can be continuously and
adequately supplied to the oil pump inlet of an automotive engine.
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6. Apparatus
6.1 Mini-Rotary Viscometer, consisting consisting of one or more viscometric cells including a calibrated rotor-stator assembly,
which are contained in a temperature-controlled aluminum block.
6.1.1 The viscometric cell has the following nominal dimensions:
Diameter of rotor 17.06 mm ± 0.08 mm
Length of rotor 20.00 mm ± 0.14 mm
Inside of diameter of cup 19.07 mm ± 0.08 mm
Radius of shaft 3.18 mm ± 0.13 mm
Radius of string 0.1 mm
6.2 Weights:
6.2.1 Yield Stress Measurement—A set of nine disks and a disk holder, each with a mass of 10 g 6 0.1 g.
6.2.2 Viscosity Measurement—Weight with mass of 150 g 6 1.0 g.
6.3 Temperature Measuring Device—Use either a DCT meeting the requirements described in 6.3.1 or liquid-in-glass
thermometers as described in 6.3.2. A calibrated DCT or calibrated low temperature liquid-in-glass thermometer shall be used as
the thermometer for temperature measurement below 25 °C independent of the instrument’s temperature control, and shall be
located in the thermowell.
NOTE 1—The display device and sensor must be correctly paired. Incorrect pairing will result in temperature measurement errors and possibly irreversible
damage to the electronics of the display.
6.3.1 Digital Contact Thermometer—Digital contact thermometer requirements:Use D02-DCT14 listed in
Criteria Minimum Requirements
DCT E2877 Class B
Temperature range –45 °C to 100 °C
Display resolution 0.1 °C minimum, preferably 0.01 °C
Sensor type RTD, such as a PRT or thermistor
Sensor, 3 mm O.D. with an sensing element less than 30 mm in length to be used with a thermowell
metal sheathed sleeve, 6 mm O.D. × 58 mm long with a ~3 mm hole in center.
Sensor, 6 mm O.D. with a sensing element less than 12 mm in length
glass sheathed
Display accuracy ±50 mK (±0.05 °C) for combined probe and sensor
Response time less than or equal to 25 s as defined in Specification E1137
Drift less than 50 mK (0.05 °C) per year
Calibration Error less than 50 mK (0.05 °C) over the range of intended use.
Calibration Range –40 °C to 85 °C
Calibration Data 4 data points evenly distributed over the range of –40 °C to –1 °C and included in calibration
report.
Calibration Report From a calibration laboratory with demonstrated competency in temperature calibration which is
traceable to a national calibration laboratory or metrology standards body
Specification D8278. As an alternative to the 3 mm metal sheathed probe noted in Specification D8278, a glass sheathed DCT
probe with a 6 mm O.D. is acceptable provided it meets the other requirements shown for D02-DCT14 in Specification
D8278. A DCT display resolution of 0.01 C is preferable. If thermowell ID is larger than the probe OD, then a metallic sleeve
must be used to fill the gap between the probe OD and thermowell ID with a length of 58 mm.
NOTE 2—With respect to DCT probe immersion depth, a procedure to determine minimum depth can be found in Guide E2877, Section 5.3, or Test
Methods E644, Section 7.
6.3.1.1 The DCT calibration drift shall be checked at least annually by either measuring the ice point or against a reference
thermometer in a constant temperature bath at the prescribed immersion depth to ensure compliance with 6.3.1. With respect to
The sole source of supply of the apparatus known to the committee at this time is Cannon Instrument Co., P.O. Box 16, State College, PA 16801. 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.
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an ice bath, Practice E563 provides guidance on the preparation and use of an ice bath. However, for this use, variance from the
specific steps, such as water source, is permitted provided preparation is consistent. The basis for the variance is due to the
reference being used to track change in calibration not verification.
NOTE 2—When a DCT’s calibration drifts in one direction over several calibration checks, that is, ice point, it may be an indication of deterioration of
the DCT.
6.3.2 For liquid-in-glass, LiG, thermometers, two are required. One LiG shall be a calibrated 76 mm partial immersion
thermometer with a scale from +5 °C to 1 degree less than the lowest test temperature in 0.2 °C subdivisions. This low temperature
LiG thermometer shall have a report of calibration showing the temperature deviation at each calibrated test temperature. The
second LiG thermometer shall be a 76 mm partial immersion thermometer graduated from at least +70 °C to 90 °C in 1 °C
subdivisions, which is used to verify the preheat temperature.
6.3.2.1 Calibration Check—Verify the low temperature thermometer at least annually against a reference thermometer in a
constant temperature bath or an ice bath. The thermometer is to be inserted to its immersion depth. If using an ice bath, the ice
point reading is to be taken within 60 min after the thermometer has been at test temperature for at least 3 min. If the corrected
temperature reading deviates from the reference thermometer or the ice point then repeat this calibration check. If the thermometer
deviates from the reference value on two successive checks then a full thermometer recalibration is needed.
6.3.2.2 Recalibration—A complete recalibration of the liquid-in-glass thermometer, while permitted, is not necessary in order to
meet the accuracy ascribed to liquid-in-glass thermometer’s design until the thermometers corrected measured temperature
deviates from the reference thermometer or ice point by one scale division, or until five years has elapsed since the last full
calibration.
6.4 Temperature Control System—Regulates the mini-rotary viscometer block temperature in accordance with the temperature
requirements described in Table X1.1.
6.5 Cell Cap—A cover inserted into the top of the viscometer cell to minimize room air circulation into the cells is required for
thermoelectrically cooled instruments. The cell cap is a stepped cylinder 38 mm 6 1 mm in length made of a low thermal
conductivity material, for example, thermoplastic such as acetyl copolymers that have known solvent resistivity and are suitable
for use between the temperature ranges of this test method. The top half is 28 mm 6 1 mm in diameter and the bottom half is 19
mm in diameter with a tolerance consistent with the cell diameter. The tolerance on the bottom half is such that it will easily fit
into cell but not allow the cap to contact the rotor shaft. The piece has a center bore of 11 mm 6 1 mm. The cap is made in two
halves to facilitate placement in the top of the cell.
6.5.1 Cell caps shall not be used in the direct refrigeration instruments, since such use would block the flow of cold, dry air into
the stators to keep them frost-free.
6.6 Supply of Dry Gas—A supply of dry filtered dry gas to minimize moisture condensation on the upper portions of the
instrument.
6.6.1 For thermoelectric cooled instruments, which use cell caps, the dry gas supply is connected to the housing cover. The supply
of dry gas is discontinued when the cover is removed for the measurement phase of the test.
6.7 Locking Pin—A device to keep the rotor from turning prematurely and able to stop the rotor at the nearest half revolution by
interaction with the rotor crossbar.
7. Reagents and Materials
7.1 Low Cloud-Point, Newtonian Oil, a a calibration oil of approximately 30 Pa·s viscosity at −20 °C for calibration of the
viscometric cells. The calibration oil shall be obtained from suppliers complying with ISO Guide 34 and ISO 17025 with
traceability to a national metrology institute (NMI).
7.2 Methanol, commercial or technical grade of dry methanol is suitable for the cooling bath.
7.3 Oil Solvent, commercial heptanes or similar solvent is suitable.
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7.4 Acetone, technical grade of acetone is suitable provided it does not leave a residue upon evaporation.
8. Sampling
8.1 A representative sample of test oil free from suspended solid material and water is necessary to obtain valid results. If the
sample in its container is received below the dew-point temperature of the room, allow to warm to room temperature before
opening.
9. Calibration and Standardization
9.1 Temperature Control Calibration Procedure—Calibrate the MRV temperature control by comparing the instruments displayed
temperature against a thermometer in the thermowell. The thermometer used shall meet the requirements in 6.3.
9.1.1 Place 10 mL of a typical test fluid and rotor in each cell. If required, place cell caps over each cell then place cover on
instrument. Cell caps shall not be used on direct refrigeration instruments (see 6.5.1).
9.1.2 Place the thermometer in the thermowell. See Note 43. This thermowell is to be used for all temperature measurements
below 25 °C.
NOTE 3—Prior to inserting the thermometer or DCT probe in the thermowell, place several drops (~3) of a heat transfer fluid such as 50/50 water/ethylene
glycol mix, CCS reference oil CL100 or a dewaxed low viscosity mineral oil in the thermowell.
9.1.3 Make the temperature measurements at 80 °C then at least three measurements that are 5 °C apart from –5 °C to the lowest
test temperature used including both end points to establish a calibration curve for this combination of thermometer and the
instrument’s temperature control. Make at least two temperature measurements at every calibration temperature with at least 10
min between observations.
NOTE 4—All temperatures in this test method refer to the actual temperature and not necessarily the indicated temperature.
9.1.4 Follow the instrument manufacturers instructions for correcting the instrument’s measured temperature. Alternatively,
establish a correction equation between thermometer and instrument’s measured temperature then adjust each temperature of the
cooling program by the offset determined with the correction equation.
9.2 Viscometer Cell Calibration—The calibration constant of each rotor/stator combination is determined at –20 °C using a
viscometric standard as a test sample.
9.2.1 The same 150 g mass is normally used for both calibration and viscosity measurements. However, different weights may be
used for calibration and viscosity measurements provided they are certified to be 150 g 6 0.1 g.
9.3 Following the steps
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