Driveshaft Angle/MPG

I put steel plate bumpers, skids, and sliders on my truck recently along with a very small lift. I just put a new scangauge on my truck and I average like 14mpg it says. I'm running the largest tires I can in an unmodified wheelwell with stock suspension and wheels.

I didn't put a carrier drop on my driveshaft (due to a 2.5" rear lift) and I have no vibration issues but could the increased angle affect my MPG that much?

 

Are you accounting for the larger tires when the Scangauge is doing that calulation? And you do realized that adding weight to the truck will eat away at MPG quickly, right??

 

What size tires are you running?

 

I'm pretty sure they are 265/75/16 Duratracs. The rear bumper didn't really add to the weight. I figured it up as probably being a 1/4 Ton of steel added to the truck. I just didn't think it would matter THAT much. I figure my tire size probably only throws the scangauge off by 1-2 mpgs but I'm no mathmatician.

 

I think you are looking at a combination of things.

Higher unsprung weight (larger/heavier tires)
Decreased aerodynamic efficiency (bumper and raised vehicle height)
Increased sprung weight (armor,bumpers)

I doubt that the driveline angle is much of a contributing factor. If the rotational resistance increased all that much I would expect your U-joints to suffer from the added wear and heat.

 

Well, you did a number of things to kill your MPG's. You have taller, heavier aggressive tread tires (I'd imagine Load Range C or D), the plate bumper, while it didn't really add much in overall weight, killed your aerodynamics, and you did add weight in armor. Combined, you get the end result of low MPG.

If you're running 265/75R16, do this next time you calculate your MPG's. 0 the trip ODO when you fill the tank up. Drive for however many miles.

Number of miles driven per ODO x 1.033 = Actual number of miles driven, corrected for taller tires.

Then divide by number of gallons used.

 

80% of your lost mileage is the lift and tires. You can get most of it back by regearing.