I 2nd what todras just said. Never in the gas, but yeah exactly as he said it has some detergents in it which will clean off some buildup in the engine. When I had my FD I would run some every so often to help fight buildup. Although it's a bit different in a rotary engine as by design they burn oil (it's injected into the combustion chamber), but the effect is all the same on a piston engine.
