In general oil and gasoline additives do little if any good and depending upon the condition of the engine (sludge, wear, etc.) they can do harm. You cannot buy a carburetor repair kit in a can or a set of lifters in a bottle. I think Dick Benjamin says it best: If you notice any improvement in performance it is probably because your wallet is lighter. Adding an additive to engine oil changes the formulation and unless you are a petroleum chemist it is best not to try to reformulate your lubricant. All the ads make it real tempting but most often there is no improvement. Rolland Westra