Quote Originally Posted by tdw6974 View Post
Have been using Mobil 1 15-50 Extended Performance. Seems like the available weights have been reduced/no longer available. Castrol Sytec seems to have more options for wt 10-40. Mobil seems to be now limited to 10-30 5-30 Now Castrol has the "edge" now available?
Tom...you didn't say if it was for a race car or your truck. I'm trying a new 10w-40 syn oil(SYNMAX) in my 98 cup car. Seems like some engineers went and looked at the properties of all the good racing oils and formulated their own. It's about the same cost as Royal Purple, a little more than Redline,less than Mobil One racing oil and way less than Joe Gibbs. All these oils have far more ZDDP(zinc) and other additives that are removed from street oil because they eat the cat. converters. Flat tappet engines(such as small block chevys,fords,etc love the ZDDP.

You could also try Brad Penn(which is the old Kendall(sp?) GT green oil which is the only Pennsylvania crude still being pumped and is green(natural) in color.