Low-Temperature Pumpability of U.S. Army Diesel Engine Oils 892053
Borderline oil-pumpability temperatures (BPTs) were determined for U.S. Army diesel engine oils by conducting diesel engine motoring experiments in a cold box. Times for pumped lubricant to reach critical components were measured in unfired engines at simulated idle speeds (600-800 rpm). The variables-investigated included: four different diesel engine types found in the U.S. Army fleet; four different oil viscosity grades; and three different viscosity index improver chemical types. In general, for a given oil, the severity of engine oil pumpability by engine type in decreasing order was; the Continental LDT-465-1C and the Cummins VTA-903T were the most severe, and were approximately equivalent. The GM 6.2L engine was the next least severe with the DDC 6V-53T engine being the overall least severe. The different viscosity index improver chemistries of specially blended test oils included: olefin copolymer (OCP), styrene-iso-prene polymer (SI), and polymethacrylate (PMA). The PMA-containing 15W-40 oils had superior low-temperature oil pumpability performance in each engine in which they were evaluated. The BPTs determined by ASTM D 3829 did not completely predict diesel engine-derived BPTs. The linear regression correlation coefficients (R-squared) resulting from the two different BPT values ranged from 0.61 to 0.88. Based on the engine-derived BPTs, recommendations for revised low-temperature use limits for MIL-L-2104 oils were made.