I put a hotshot intake on my car and put the 15's back on for the winter and i'm getting bad gas mileage. I was getting an estimated 25mpg with the 18's (estimate because my odometer is wrong with the bigger tires) and now I'm getting 20 if I'm lucky. They put the mtbe stuff in the gas during the summer only, right? Maybe it's just cause I'm riding it harder now to check the performance with the intake, but shouldn't the intake give better mileage as well?