Explain Why Mobil 1 Extended Performance Not GM4718M Certified Can you please explain the difference between GM6049M and GM4718M? I have read several answers on this site that state that using the extended performance Mobil 1 will work just as well as regular Mobil 1. I just want to understand what is different between the two specs, and what about the extended performance does not allow it to be GM4718M certified. Thanks, Clint -- Clint Kline, Anderson, IN Answer: GM 6094M is based on the same specifications as ILSAC GF-4 but additionally includes some specific GM requirements. GM 4718M is the GM high performance oil specification that goes well beyond the industry standard ILSAC GF-4 and API SM specifications. The Mobil 1 grades that carry GM 4718M have been fully approved and tested against GM 4718M. The companion Mobil 1 Extended Performance viscosity grades have not been formally approved against GM 4718M but will provide the performance at GM 4718M level. Engine testing required to get formal approval is limited to certain Mobil 1 products only.