Lucas upper cylinder lubricant is better than STP, more expensive but its better... not to thread jack sorry. We have Fred Meyers out here which is Kroger. my girlfriend works for them and she won't buy gas unless its premium or at bare minimum mid grade. I have had bad gas from shell and 76 so i like to go to Chevron if at all possible. with funds lately i been putting cheap freddy's gas in and crying all the way home...