E36 M3oil The BMW spec is 15W40 non-synthetic.
Browsing my local Auto parts store, whose computer confirms the grade for my E36, all the 15W40 oils on the shelf are labelled "for diesel engines". I shuddered at the prospect of putting the "wrong" oil in an M3, so I just went and bought a case from a BMW dealer. At less than $3 a quart I will probably do the same again. But I'm curious.
Other than the additives that oil manufacturers use to claim superiority over rivals, are oils with the same SAE classification basically the same?