I put in the Prestone fuel injection cleaner about 2 days ago and I can already feel a change. If you've got 4 bucks layin' around, go buy a bottle and throw it in with a tank of gas. Especially if you have a car with high mileage. They have a mixture of the cleaner and an octane additive that takes care of any knocking or pinging you might have too. Two thumbs up on this stuff.