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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.

Concern about the consequences of fuel dilution on engine oil properties are intensifying due to the increasing use of E25 and E85 fuel in passenger cars. Notably, such concerns are about the effect of emulsion formation and stability in crankcase oils by E25 or E85 fuel and water dilution on vehicle operation at cold-start conditions. Different types of Viscosity Index Improver (VII) chemistries were evaluated for their effects on emulsion formation and engine oil characteristics. Emulsions were prepared with fresh and used passenger car motor oils using the ASTM D7563 method for emulsion retention. The emulsion properties were evaluated after storage for 24 hours at two different temperatures. Separate oil/gasoline and emulsion (ethanol/water/oil) phases were observed for fresh oil emulsions. None of the emulsions exhibited a separate water phase, regardless of the type of VII in the oil.