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In 1999 the ASTM Low Temperature Rheology of Used Engine Oils or LOTRUO task force was formed within Subcommittee D02.07 to address potential method and measurement issues for low temperature rheological determinations of used engine oils. A primary focus of this task force was to assist the heavy duty engine oil classification panel which was developing the new PC-9 category, to include a used oil pumpability specification from one of the new multicylinder EGR diesel engine tests. With anticipated soot loadings of 5-10% in some of these used oils, there was concern that standard ASTM test methods developed for fresh oil pumpability might not be suitable for these sooted oils. The task force conducted some preliminary work on a used Mack T8E test sample of approximately 5% soot loading. These data indicated that variation in preheating conditions could have significant influence on the low temperature properties measured by standard procedures.

Modern vehicles are expected to operate satisfactorily at relatively low ambient temperatures, often without auxillary heating equipment. At these cold temperatures, the lubricant plays a key role in determining how easily the vehicle can be started, and how quickly all vital moving parts are oiled. A lubricant which is too thick under these conditions may result in poor operability, or in some cases catastrophic equipment failure due to oil starvation. Extensive testing has demonstrated the low temperature performance advantages of SAE 0W-30 or 5W-30 engine oils versus more common SAE 10W-30 and 15W-40 viscosities, in both light and heavy duty engines. Automatic transmission fluids with enhanced low temperature properties have shown faster start-up flow and in some cases, more rapid shift times. Hydraulic fluids with improved cold flow performance allow more rapid equipment warm-up and faster response at low temperatures.

The cold starting and low temperature pumpability performance of twenty-one new and used multigrade oil formulations was determined in fired engine tests conducted with Caterpillar 3406B, Cummins NTC-365 and Detroit Diesel S-60 heavy duty engines. Viscosity grades included SAE 0W-30, 5W-40, 10W-30, 10W-40 and 15W-40, formulated with various commercial viscosity index improvers (VII's) including olefin copolymer (OCP), dispersant multifunctional olefin copolymer (MFOCP), polymethacrylate (PMA) and styrene-isoprene copolymer (SICP). Significant differences in pumpability characteristics were observed among the test engines, but there was no evidence of pumpability problems with the oils evaluated. In fact, significant pressurization of the oil delivery system occurred during engine cranking, prior to ignition. Good correlations were observed between the MRV test oil viscosities and pumpability characteristics in the test engines, both on an individual and on an average engine basis.

The low temperature pumpability performance of twenty-one new and used multigrade oil formulations was determined in fired engine tests conducted with Caterpillar 3406B, Cummins NTC-365 and Detroit Diesel Series 60 heavy duty diesel engines. Significant differences in pumpability characteristics were observed among the test engines, but there was no evidence of pumpability problems in the oils evaluated. In fact, significant pressurization of the oil delivery system occurred during the engine cranking phase, prior to ignition. A comparison of different SAE “W” viscosity grades indicated pumpability characteristics consistent with the J-300 classification system. Good correlations were observed between the MRV viscosity of the test oils and pumpability characteristics in the test engines, both on an individual, and on an average engine basis.