I just recently advanced my timing to 15 degrees and adjusted my valves and think I am getting fairly decent mileage with my 12valve. I also pushed my fuel plate half forward for a little extra fuel. This truck now really accelerates harder from 3rd gear on now. I was used to my timing being at 7 degrees before last weekend, so it really feels like a new truck to me. Anyhow, I left at 5am yesterday morning for a 4 hr road trip, now keep in mind it was 2 degrees outside when we left and the truck still got 19 miles per gallon running 75-77mph avg. Hows that compare to everyone elses?