I noticed the gas milage falling off in my car so i decided to go down to kragen and pick up some valvoline fuel system cleaner. It was like $8 and said only have to do it once a year. Im on my first tank after the cleaner was added and the cars seems more powerful but could be just my backside fooling me. Now im at about 200 miles with half a tank still left. Before it would get about 250 before i had to refill.