Years ago I put some STP oil treatment in my Briggs and Stratton on the old mini-bike. It started running poorly, and when I opened it up, it was gunked up with white stuff, semi-bonded to the metal. It could've been too much I suppose, but I havent used an oil treatment since- Multiple quick oil changes can do miracles with high mileage even badly smoking motors. And I ALWAYS run distilate carb and /or injection cleaner in the tank. Those really work.