When my father bought his Pontiac new in 93 I put it on synthetic oil after proper break-in. The engine (3.3) calls for 10w30 year round. It gets changed twice a year (approx. 4 to 6k between changes). I have used a number of different brands over the years but have been using M1 for the last few years since all the other PAO oils (store brands) have disappeared. In its early days it got AMOCO Ultimate syn. which was available at K-mart at the time. It also got Western Auto which I believe was Texaco. It has had Pennzoil Performax and also Exxon Superflo syn. I know from a previous post that Performax was highly regarded. Does anybody have any thoughts on these other brands that I mentioned in particular the AMOCO Ultimate syn SG rated and the Exxon Superflo syn SJ rated which it was fed many times. Thanks.