I guess my question is what do you expect it to do? I have used it for older engines with sticking lifters, pour in the oil a few hundred miles before an oil change to help clean varnish, sometimes it works. Carbon build up in combustion chambers, induce into the engine, carb, throttle body or a vacuum port, yes it helps knock carbon loose. Never used it as preventive maintenance in fuel tank, but would not hurt. Just don't think it's a magic wand.