You have a 3.9, and a clean filter is always better than a dirty one.Bigguy18LSU77 said:what kind of gas mileage do you guys get? I'm getting around 16mpg in regular driving. I have the Airaid intake and dynaflow exhaust as well, but it doesn't seem to be helping me any. I have a 1997 dak extended cab. Don't know if it is a 3.7 or 3.9 I also have new plugs and wires and rotory on it. The filter is dirty, but that shouldn't drop my mpg should it?