This test method determines the suitability of fluids like automatic transmission fluids, gear oils, hydraulic fluids, and other lubricants for use at low ambient temperatures, while covering a viscosity range of 300 mPa·s to 900,000 mPa·s. The standard describes four different procedures, A, B, C, D, each requiring a different configuration. Procedure D is an automated test method, which means that it is performed automatically with only one instrument configuration.
ASTM D2983 – Standard test method for low-temperature viscosity of automatic transmission fluids, hydraulic fluids, and lubricants using a rotational viscometer
Why measure the viscosity of lubricants at low temperatures?
The viscosity of lubricants plays a major role for the proper operation of mechanical devices used at low ambient temperatures such as -40 °C or -20 °C. Under such demanding conditions, lubricants must guarantee a sufficiently low viscosity, so that the lube is still able to flow. The viscosity has to be analyzed at the minimum temperature at which the lube is still applicable to ensure adequate lubrication of critical parts. The standard SAE J300 states a critical viscosity of >150,000 mPa·s at which flow problems and pinion bearing failures can occur.⁽¹⁾
What are the requirements for viscosity measurement according to ASTM D2983?⁽²⁾
Rotational viscometer
- Procedure A, B, C require a rotational viscometer having a torque range between 0.0670 mNm and 0.0680 mNm.
- Procedure D needs a programmable rotational viscometer having a torque range between 0.0670 mNm and 0.1800 mNm.
For viscosity measurements, the viscometer must at least have the following speeds available:
- 0.6 rpm
- 1.5 rpm
- 3.0 rpm
- 6.0 rpm
- 12.0 rpm
- 30.0 rpm
- 60.0 rpm
- 120 rpm is desirable for procedure A to C and mandatory for procedure D
Temperature control units
The choice of temperature control unit depends on the test procedure. Samples are cooled as follows:
- Procedure A: with an air bath to test temperature
- Procedure B: with a mechanical refrigerated programmable liquid bath
- Procedure C: with a mechanical refrigerated constant temperature liquid bath by means of a simulated air cell (SimAir)
- Procedure D: with a thermo-electric temperature-controlled chamber in a range from -45 °C to +90 °C
Measuring system
Figure 1 Viscometer spindle for ASTM D2983. A = uninsulated steel spindle; B = insulated steel spindle
Viscometer spindle:
Procedures A, B, C, and D require a cylindrical viscometer spindle with the same geometry.
- An uninsulated steel spindle (Figure 1, A) should be used only for procedure A.
- A composite spindle, which has lower thermal conductivity, must be used for procedure C.
- A spindle with insulation on top (Figure 1, B) is required for procedure D.
Test tubes:
- Procedures A and B: standard test tube with approx. 25 mm ID and 115 mm in length, and 30 mL of sample volume
- Procedure C: special SimAir Stator with 15 mm ID, and 15 mL of sample volume
- Procedure D: test tube with approx. 25 mm OD and 150 mm in length, and 20 mL of sample volume
Common units
According to the ASTM standard, dynamic viscosity must be indicated in millipascal seconds [mPa·s].
Other relevant standards for rotational viscosity testing of lubricants at low temperatures
ASTM D8210: Standard test method for automatic determination of low-temperature viscosity of automatic transmission fluids, hydraulic fluids, and lubricants using a rotational viscometer
DIN 51398: Testing of lubricants; procedure for measurement of low- temperature apparent viscosity by means of the Brookfield viscometer (liquid bath method)
ASTM D5133: Standard test method for low temperature, low shear rate, viscosity/temperature dependence of lubricating oils using a temperature-scanning technique
ASTM D7110: Standard test method for determining the viscosity-temperature relationship of used and scoot-containing engine oils at low temperatures
What is the difference between ASTM D2983 and D8210?⁽³⁾
ASTM D8210 describes a test method which is equivalent to procedure D from ASTM D2983. According to ASTM D8210, this test procedure is called “Option A – Standard Thermal Conditioning”. Procedure D from ASTM D2983 and Option A from ASTM D8210 include the following main steps:
- Preheating the sample to 50 °C
- Cooling to room temperature
- Cooling to test temperature according to Newton’s cooling law (Equation 1)
- Keeping at test temperature for a period of time (~14 h)
- Viscosity measurement at several speeds
$$ST= (C *{e^{k*(ET-PT)}*{5 \over 9}})+T$$
ST = Segment after preheating and returning to room temperature, °C
ET = Elapsed time since the beginning of the test, minutes
PT = Preheating time includes the time to bring the sample to preheating temperature, soak time, and return to room temperature, minutes
T = Test temperature, °C
C = 102
K = -0.08
Equation 1: Application of Newton’s cooling law in order to cool the sample to test temperature according to ASTM D2983
The difference between these standards is that ASTM D8210 additionally describes an automated test method with a reduced thermal conditioning phase. This procedure is called “Option B – Abbreviated thermal conditioning”. The holding time at test temperature before the viscosity measurement starts is reduced from ~14 h to ~4 h. Shortening the thermal conditioning time can result in a lower viscosity value than that measured with the standard method.