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The SAE Engine Oil Viscosity Classification (EOVC) Task Force has been gathering data in consideration of extending SAE J300 to include engine oils with high temperature, high shear rate (HTHS) viscosity below the current minimum of 2.6 mPa⋅s for the SAE 20 grade. The driving force for doing so is fuel economy, although it is widely recognized that hardware durability can suffer if HTHS viscosity is too low. Several Japanese OEMs have expressed interest in revising SAE J300 to allow official designation of an engine oil viscosity category with HTHS viscosity below 2.6 mPa⋅s to enable the development of ultra-low-friction engines in the future. This paper summarizes the work of the SAE EOVC Low Viscosity Grade Working Group comprising members from OEMs, oil companies, additive companies and instrument manufacturers to explore adoption of one or more new viscosity grades.

The new API CI-4 category defines oil quality suitable for 2002 EGR-equipped heavy duty diesel engines. Included in the category is the first used oil low temperature MRV (Mini-Rotary Viscosity) limit. Over the past 15 years heavy duty pumpability studies have been the focus of a number of studies but few have evaluated used engine oils, particularly at the high soot loadings expected in EGR-equipped engines. To gain a better understanding of rheological effect, Imperial Oil initiated fired pumpability tests of sooted and fresh oils. Three 1999 model year Class 8 heavy duty diesel trucks equipped with engines from three popular manufacturers were chosen for the study conducted in Imperial Oil's All-Weather Chassis Dynamometer. Fresh 15W-40's were compared to used 15W-40 oils taken from severe line-haul service where soot loadings were in the 6-7% range; limited testing was also conducted on a fresh 0W-40 formulation.

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.