A ways back when I put 285s on my truck, I simply removed the black air dam that attaches to the metal bumper to keep it from rubbing. Of course, this was back when diesel was cheaper than gasoline, and as we all know times have changed. My question is, If I trim and reinstall the air dam, will I see better fuel economy. Im seeing 16 mpg loaded and around 18-19 mpg unloaded, all hand calculated. When I got the truck, with the pizza cutter wheels, I was seeing around 23 mpg unloaded (its a regular cab). Do the 285s make that big of a difference, or is my snaggle-toothed front end to blame?

Both. I know a guy who has a Ford 350 Powerstroke who went to the extreme and bought some conveyor belt and tacked it onto his bumper - it runs down within 1.5 inches of the road... and he claims it bought him a good increase in mileage (don't remember exactly how much right this moment). There are some studies that back this idea up. The difficulty is ground clearance. Dave has some framework supporting the conveyor belt down to 3-4 inches above the deck and he figures the belt is tough enough to handle the rest. Take a look at big trucks and see just how low their bumpers/valences go.

The pizza cutters also have less rotational mass, so it takes more to turn them. Unlike aerodynamics (which kick in at modest-to-highway speeds), turning those wheels just takes more power... all the time.

I decided yesterday to go ahead and trim and reinstall the front air dam...No word on the milage yet, but I noticed the engine is running about 15-20 degrees cooler. My water temps used to be on the 210 line at all times. Since reinstalling the air dam, its been running at about 2-3 ticks before the 210 line.

I decided yesterday to go ahead and trim and reinstall the front air dam...No word on the milage yet, but I noticed the engine is running about 15-20 degrees cooler. My water temps used to be on the 210 line at all times. Since reinstalling the air dam, its been running at about 2-3 ticks before the 210 line.

Did you notice your fan kicking on a lot more with the valance off? If it runs near 210*, the fan clutch might engage more often, and this would have a negative impact on your mpg, in addition to aero losses.

First highway tank with the air dam back on I got 18.1 mpg. No change whatsoever. I guess the 285 BFG Mud terrains with the high void really does kill your milage. I never thought it would be a 4-5 mpg difference though. Time to go tire shopping it looks like.

I used to get great mileage with stock tires (the same as yours) when I put my bfg muds on (35s mind you), I dropped down to about 18 at best on the highway... usually about 16. I know the lift and bigger tires hurt mileage, but i think the muds seem to hurt it even worse.

Im goona have to agree. When I put even BFG A/Ts on my old 350 gasser it didnt impact the milage a noticeable bit, but 4-5 mpg is killin me. Luckily I already have about 26k on these tires, so they should be coming off in another 10k. I think I'll go back to All Terrains even though they don't do nearly as weel in the mud. Either that or 255/85/16 If I can find a tread pattern I like.

think about using a programmer? I lost big time when I twisted my bars up and install the new toyos, about 3-4mpg from when I bought it with worn out undersized 315s and nosedive stance. I have recently added a predator @ 60hp and have seemed to be getting that mileage back with still pretty aggressive driving. I still have to run a few more tanks through her and do some highway trips but so far so good.

Yeah I am trying to decide between PPE Standard and EFI Live. I like the idea of EFI Live but don't know if I wanna mess with it. PPE is cheap and easy but I can't do stuff like change the turbo vanes at idle and make girls clothes come off like with EFI Live (at least I think there is a way to do that eith EFI)

this is what prompted me to get mud terrains in the first place

I got stuck in very shallow mud with those stockers, but I also got some ladies to pose on my truck with those stockers after another exciting trek through mud with pizza cutters for tires