Originally Posted by finklejag
Most of Mobil 1 oils are mixed group III/IV these days. Even Amsoil's OE and XL lines are group III.
I'm confident that the Amsoil OE I'm using, on a 5k mile OCI, will serve my car well for its lifetime. But when I do my next oil change in 4k miles (with the odometer at approximately 12k miles), I plan to send a sample into Blackstone for an analysis, just to make sure.