Seafoam is a top cleaner sold at the auto parts stores. In the gas tank it helps melt the varnish and buildup away from metering holes & injectors. Directly into hot idling carb or throttle body (whole can then shutoff & soak for 1hr) will remove carbon from tops of pistons & back of valves. I stock up at Advanced Auto when it goes on sale. Lot of people swear by it and call it a tune up in a can. All my vehicles are addicted to it - especially my 300C.