Well I just put Syntec in the Buick. I'm sure the General would be appalled, but no warranty at 80K anyway. I'm impressed with the spec's of this oil enough to try it. I've never bought the argument that this engine like a thicker oil, but this is a very thin 40wt. and I like the add pak. I wanted to see how it compares with M1 10-30 for me.