Marginal. I do a lot of around-town driving, so my gas mileage kind of sucks, regardless. That, and I tend to have a heavy foot. (I love the way it sounds, sorry!) But I'm getting around 30.2 right now, give or take. And that's with 95% (at least) city driving. On my way out to the Outer Banks in early October, I averaged 38+ mpg. So from what I was getting before the exhaust and intake, I guess I've actually gained about 3 mpg city, and 4 mpg highway.