Low Temperature Performance of Commercial SAE 5W-30 Oils in Engines and Their Correlation with Bench Tests

A 2.3 Liter, overhead cam engine was motored in a sub-zero temperature room to measure the flow characteristics of several SAE 5W-30 commercial lubricants. The lubricant pressure and rate of pressure rise were measured at 8 different points in the engine. The engine was cooled either by an extended overnight cooling program or a constant cooling rate program. These cooling programs were similar to those used in ASTM D4684 and D5133 respectively. During each test the power to motor the engine, as well as the lubricant pressurization time was monitored. A video record was made of each of the tests for later review.

In these tests, a correlation was found between lubricant pressurization time and pumping viscosity as measured by the bench test methods, ASTM D4684 and D5133. Significant differences were found between the engine's response to an oil and its ranking by the pumping viscosity bench tests. None of the SAE 5W-30 oils tested failed to pump in this engine at -35 °C, which is 5 °C below the specification temperature expressed in SAE J300. However, some oils took longer than 2 minutes to fully pressurize the cam towers. Several oils exhibited a pressure drop in the engine lubricant system after the filter for several seconds. However, no corresponding pressure loss was seen at the oil pump or in the oil pickup arm for the SAE 5W-30 oils.