Cold Starting and Pumpability Studies in Modern Engines — Results from the ASTM D02.07C Low Temperature Engine Performance Task Force Activities: Phase II Pumpability Testing

Abstract

The Low Temperature Engine Performance Task Force Phase II pumpability test program focused on the evaluation of six engine oils which exhibited significant yield stress or gelation index in slow-cool bench tests. The test oils were designed specifically to have abnormal flow properties and are considered to be non-commercial formulations. The light duty engines that primarily were used included the 2.2L I-4, 3.8L V-6, 4.0L I-6 and 4.6L V-8 engine, with some additional work in the 2.3L I-4, 1.9L I-4 and 3.0L V-6. Four laboratories contributed work, and each used different engines, and often, different cooling profiles, in attempts to better establish the importance of yield stress and gelation index to air-binding failures in modern engines. For the majority of Phase II oils tested, air-binding failures were not detected. No pumping failures were detected with the phase II test oil LTEP 23, which had a gelation index of 16. Using the 4.6L V8 engine, an air-binding failure was detected only with LTEP 27, an oil that had caused air-binding failures in other work. The 2.2L I-4 engine did not fail by air-binding, but the 3.8L V-6 and 4.0L I-6 engines, which generally exhibit flow-limited failures, were “tricked” into producing air-binding failures by use of a reduced volume of test oil LTEP 28. This oil exhibited a gelation index of 40; it also exhibited a substantial yield stress (70–105 Pa) and a relatively low pumping viscosity when the engine pumping tests were run.