Drove down from Big Bear mt here is SoCal. The trip down hill was 20 miles and I really picked up some MPG's. It quickly dropped as I hit the freeway. The next 140 miles was all hilly freeway. Still averaged nearly 20MPG. So what you say, well my JKUR is on 35's, 4.10's, with plastic undercover removed. I usually average 19 on the freeway but the new Banks intake bumped me up a MPG maybe 2. Now my computer is 1MPG proud, so I always do the math to be sure. Good driving habits.