I have used a lot of Lucas products, and none of them will give you a miracle fix like that. If it actually made a 5-10 mpg difference they would be just as greedy as "big oil" and would be charging a million dollars a bottle...lol. Although I do use a Lucas product that has some amazing results...Lucas ethanol eliminator. It actually increases my mpg. My '87 Wrangler has a new 4.2L that is carbed, with 8.5 inches of lift, 4.56 gears, ax15 5spd, and riding on 35's and it is getting a religious 18mpg all the time. So i cant complain and i will continue to use my Lucas products.