i use penzoil and my ENGINE runs fine, you go any more expensive and thats synthetics which you don't HAVE to change until longer miles. well unless your talking about mobil 1 which i have no experience with. all in all i doubt going from penzoil to a more expensive oil will fix your current problem. and i think by cheap oil they meant 50 cent a quart sludge. i'm no mechanic so anything about oil pumps or whatever i wouldn't know about.