5.1 The low-temperature, low-shear-rate viscosity of automatic transmission fluids, gear oils, torque and tractor fluids, power steering fluids, and hydraulic oils are of considerable importance to the proper operation of many mechanical devices. Low-temperature viscosity limits of these fluids are often specified to ensure their suitability for use and are cited in many specifications.

5.2 The manual test method, Test Method D2983, was developed to determine whether an automatic transmission fluid (ATF) would meet low-temperature performance criterion originally defined using a particular model viscometer.4 The viscosity range covered in the original ATF performance correlation studies was from less than 1000 mPa·s to more than 60 000 mPa·s. The success of the ATF correlation and the development of this test method has over time been applied to other fluids and lubricants such as gear oils, hydraulic fluids, and so forth.

5.3 The viscosity determined by this test method using option A was found to be statistically indistinguishable from Test Method D2983 – 16 measurements based on the ILS data to establish this test method’s precision.

5.4 Due to the shorter time at test temperature, results from the abbreviated thermal conditioning (Option B) may differ from results obtained with the 14 h soak at test temperature (Option A). For the samples used in developing this test method, results obtained with the abbreviated procedure (Option B) tended to be less than 14 h soak (Option A). This difference seemed to be larger for products that contained high wax base stock.