I've tried all the other regular stuff before, but seafoam seams to work much better at getting rid of carbon deposits - the thing you want to remove in the first place from your engine. As long as you don't have any engine running issues right now, it would be good enough to just throw in a can of this stuff per 5 gallons of gas... so about 1 and a half cans will do it for a tank. Try to drive a lot of freeway - this works best since the engine is hot and will more likely burn off the accumulated carbon.