i am wondering what the best kind of oil for performance is...i'm using full sythetic, and would like to keep it that way..right now it has 10w-40 in it...i was thinking of bumping it up to 20w-50 here soon...would that be a good idea or no..if no, what should i put in there in stead (84 z-28 111k miles)

 

Just my opinion, but if you are maintaing adequate pressure at elevated temperatures with the 10W40, there should be no need to increase the viscosity. It may only cause a waste of pumping power. If you want to try an intermediate range, Mobil 1 has 15W50.