What GM dexos2 means
GM dexos2 is an engine oil specification developed by General Motors (GM). The dexos family sets performance and approval requirements for oils used in GM engines, and an oil that meets a dexos specification has been formulated and tested to that standard. The dexos2 specification is associated with many diesel engines and some European GM gasoline engines, reflecting the requirements of those applications.
A specification like dexos2 is separate from the viscosity grade, such as 5W-30. The dexos approval describes the oil’s performance and that it has met GM’s requirements, while the grade describes how the oil flows at different temperatures. An oil for your engine should meet both the specification and the grade your manual lists.
dexos2 and dexos1 are distinct
GM uses more than one dexos specification, and they are not interchangeable. In general terms, dexos1 is specified for gasoline engines, while dexos2 applies to many diesel engines and some European GM applications. Because the two have different requirements, an oil approved to one is not automatically suitable where the other is specified.
GM has updated its dexos specifications over time, so the exact designation your engine needs depends on the vehicle and what the manufacturer states. Rather than assuming that any dexos oil will do, match the specific dexos type called out for your engine.
What to follow
Your owner’s manual is the authority on which dexos specification and viscosity grade your engine requires. If it lists dexos2, choose an oil that carries that approval in the correct grade, and confirm any substitution against the manual before use.