'99 Chevy 454 mileage

I have '99 chevy 3500 dually.Does anyone know of anything that can be done to improve mileage on this thing? Right now, I am getting about 8mpg. Any info is appreciated...thanx

I am also looking for mileage improvements; '98 Sily 5.7 Vortec. Please post mileage ideas, if anyone has seen something that works.

I put a k&n filter & a hot computer chip for about a 10%gain in mpg.Chip was 120. filter was 40.Make sure you have a good tune up & you get a little better.My truck is a 4x4 silverado ext.cab 5.7 It pulls 25 foot 5th whl & gets about 13 or 14 mpg LOADED.Unloaded I get about 17 or 18 mpg.Remember on big trucks bad tires can wreck your mpg.Make sure your wheel bearings, brakes,and drive line are in good shape & lubed up full.Drive that big block like a kitten & watch your mpg go up!!