Synthetic Mobil One?
For a modern street engine and a roller race engine, that is all I would use. As for the weight that would be dictated by the application and the piston to wall clearance. Todays motors are built tighter than the old stuff. That's why the trend are going
5-W and 0-W.
As for the change at 10,000 miles or in the case with
Amsoil, yhe 35,000 to 100,000....Don't buy it. I am not saying the
oil can't do that without breaking down but what about the other most important item??? THE FILTER??? I hope none of you keep a $5 Dollar filter on a 35,000 mile
oil change.
As for those of you running old world big blocks with solid lifter cams. In my opinion, no
synthetic at all. Forget what Nascar does. The need slippery and fast. They also use a fresh motor for every race. Your solid lifter cams will live longer on the track with either Nascar 76 20-W-50 or Pennzoil Racing 25W50. Forget the rest. The 2 I mentioned are the only conventional oils with the good stuff in them.
Remember,
Oil companies do not have a huge need to make the right oil for the old solid lifter stuff.