I changed my air flter and then went to cerami isuzu to get my wheels aligned, wheel bearings greased, and all the 4x4 parts fluids flushed.. 450 bucks. I went from 17 hwy to about 19.5.... and that lasted a while.. It's now down to 16-17 hwy and that's after I upgraded the exhaust. Expect to get less mileage in the winter as an additive is used in your gas for cold weather operations. Also, check the tire pressure since 29 is the require pressure. This is import more for the TOD than the mpg..... my transfer case went bad, but I'd like to thank Cerami for warrenty work cost me nil! I was expecting to get 20-21 hwy with the new exhaust, but now with winter it's hard to tell exactly.