I use synthetic fluids, change fuel & air filter frequently run 36# air presure in tires and I never get less then 18 but on the high I get 20 to 21. Now I just tried something on my run from Des Moines to Omaha today, I put 4 oz of acetone in my fuel, crazy or not i tried it, I felt better perf...

I have a 98 Astro with 168,000 miles, with using syntheic fluids, keep the OEM air filter changed every 10,000, fuel filter every 30,000, have my tranny flushed every 50,000 anc change my diff fluid every 50,000, keep tires at 35 lbs with valve tattle tales, I get 18 mpg in town and 20 to 21 on the...