Study on Fuel-Saving Durability of Ultra-Low Viscosity 0W-8 Gasoline Engine Oil

The JASO GLV-1 standard was introduced in Japan for 0W-8 ultra-low viscosity gasoline engine oil to improve fuel economy. Fuel economy targets are specified for new oil but not for aged oil. In contrast, Sequence VI in the ILSAC GF-6 standard requires fuel economy improvement for both new and aged oils. This test simulates fuel economy improvement after 6400 km (FEI 1) and 16000 km (FEI 2) of driving based on US fuel economy certification testing. Currently, 0W-8 is not included in the ILSAC standard and the fuel-saving durability of 0W-8 has not been investigated. To include ultra-low viscosity oil like 0W-8 in future engine oil standards, it is necessary to know its fuel-saving durability and to examine the evaluation test method. This study focused on the fuel-saving durability of 0W-8 with or without the Mo friction modifier and considered the evaluation method. Sequence VIF tests, JASO M365 MR20DD motored fuel economy tests and actual vehicle fuel economy tests involving 16000 km of driving were conducted to investigate the fuel-saving durability of 0W-8. The results show that (1) fuel-saving durability in the MR20DD motored test using engine oil aged by laboratory oxidation displayed the same tendencies as fuel-saving durability in Sequence VIF tests. This test method shows good potential for evaluating fuel-saving durability. (2) Fuel economy improvement after 16000 km of driving was better than the initial fuel economy improvement with or without the Mo friction modifier. This tendency differed from the results of previous studies of 0W-8 in Sequence VIF tests cited in this paper and the reason is presumed to be differences in the engine valve train system and coatings.