[Big Dave]

Glad to see someone taking an integrated approach to pickup MPG. Too many guys are “hammers” and see all the (pickup) world as a “nail.” Engine guys think only in terms of engine mods. Body men think in terms of aero mods, etc. The right answer is “all of the above.”

You might help us help you by burning a brain cell or two in describing what you intend to do with the truck. Cars are naturally single-purpose vehicles but the very soul of a pickup is versatility. Do you tow a lot of (like me) intermittently? Are you a commercial operator who has to drive around with a bed full of stuff all the time, or do you just haul butt? Give it some thought and fill us in.

What you do with the truck also speaks to weight management strategies. You could beat your brains out reducing weight and then defeat yourself by hauling heavy loads in the bed. You live in hilly country but where I live (central Indiana) is as flat as pool table. Kansas looks mountainous by comparison. Weight and grade interact vigorously in the road load equation. Thus weight is crucial for you, but me…not so much. Good thing. My sturdy Ford is heavy. Sadly, the two adjectives often go together.


Like you, I wish Bondo was having better success. Have you ever seen the youtube clip of his aerolid in a wind tunnel? Baby, that’s the gold standard. The smoke tells me his laminar layer stuck tightly all the way down the lid to the cut-off edge. Add in his outstanding workmanship and I would have paid good money for his stuff. But he’s right. These are not good days for startup manufacturers. But in the interim, I wouldn’t be too ashamed to have a good DIY-looking aerolid. Phil Knox (aerohead) is certainly not in bondo’s class as a fabricator, but his air flow obviously likes his truck. A number of guys seem to be teaching themselves fabrication skills making aerolids. My old aerolid looked hideous but worked like a champ. I could immediately tell it was working because the wind noise dropped to nearly nothing. Once you’ve got a handle on what you are doing read the various threads about DIY aerolids. We’ve all made our mistakes and learned from them. Mine was too steep, had no working hatch and was utterly opaque to the rear. I’ll address that on my next try.

Your truck is classicly over-geared. You can tell its over-geared because its MPG is not sensitive to other changes. I can tell I’m nearly at the optimum because every little thing affects my MPG.

Tires. What size are your tires? I’ve done some experimenting both ways and have come to the conclusion that tire selection is one thing the factory boys have a handle on. My truck’s optimum tire has a 31.7 inch outside diameter. Go down in diameter (without going to unobtainable gear ratios) speeds up the engine and the engine frictional HP eats up your MPG. Go up in diameter and the rotational moment of inertia takes a bite out of your MPG every time you accelerate away from a stop. Do you need gnarly off-road tires? Some do. Some don’t. I use road only tires, but I’m in a 4x2 use regime and can get away with it. So the times I get off pavement I have to be touchy where I go. Not a big deal to me but it might be to you. I also inflate my tires (they’re Firestones and you don’t dare under-inflate Firestones) to 25% over the sidewall max number. Anytime tire pressure drops, I notice a drop in MPG.

Watch your brakes and wheel alignment. My ford tends to drag the rear discs and that robs you of MPG. I put little springs in the calipers to promote good disengagement. I don’t know how much your 4x4 can do this but if you minimize toe-in, it reduces front tire drag. Early Honda Insights had zero toe-in and obviously Honda was leaving no stone unturned. Zero toe-in sacrifices the self-centering tendency of Ackermann steering so you have to positively hand-drive the vehicle every inch of the way. I think only Wayne Gerdes can live with this constant strain because he is so committed to getting good MPG.

Evans waterless coolant. I use it and my testing showed it improved my MPG by 0.5 MPG in an already high MPG truck. I also went to a 203 degree stat (fairly available for 7.3 Powerstrokes). This is good on-balance but be aware: At defroster on full-blast (I was fighting freezing rain) 203 degrees can crack windshields and cook your fingers if the heater vents blow on them. When converting be sure and get all the water out of the cooling system. Use a heat gun to get the last bit out of the block. I got lazy and my Evans turned black. Seems to work OK but I hate the look. I went to Evans to defeat cooling jacket cavitation. The 7.3 Powerstroke is an old school-bus motor and it has a fearsome water pump. It flows so much water that 7.3s have been known to cavitation-erode the front two jackets completely through. From the factory mine needed a maintenance-intensive water treatment. The Evans boils over 400 degrees so cavitation is no longer an issue. I’ve never heard of that being an issue to BT3.9 engines.

You have a lot of scope for improvement, and if you re-gear, you’ll remove a big obstacle.