I don't want this to sound bad, but I don't understand people who get into this hobby, have a nice car with a lot of money invested and then worry about gas mileage. I realize the Op in no way indicated that he was worried about gas mileage. I'm not referring to him. I get about 10 MPG in town and about 14-15 on the highway with my moderately built 340 4 speed and 3.55 gears. I am fine with that. I look at it as 10 Smiles Per Gallon in town Now if the mileage went down to 5 MPG in town, I would worry about what the problem was that caused a drastic reduction in MPG and fix it.