NPC5515

Hey guys, I was wondering if replacing my stock bumper on my '13 with a n-Fab RSP Prerunner bumper would hurt my fuel economy. I don't have a crazy lift, just slightly bigger tires so my current fuel economy is pretty similar to stock; anyone have any insight? Thanks!
-Neil

patclarke

Im not %100 sure but I would think more weight so it would be slightly less. I don't think You would be able to notice the decrees in MPG.

NPC5515

Ok, I wasn't worried so much about the weight as the fact that more air would be flowing under the truck (due to the skid plate acting like a wing), which is why lifted trucks get worse mpg. Thanks!

patclarke

I think you would have to be going fairly fast for it to make a huge difference (again I could be wrong). I have a custom made "Prerunner Bumper". I'm not sure what my MPG was like before it, but with it and 4.88 gears 37x12.5R17 KM2's K&N intake I get about 12.5 MPG at about 75MPH on a flat surface. O and my engine is the 5.4L Triton V8. Hope that helps.

uzikaduzi

you are right that air flowing underneath the truck disrupts the flow of air over the cab. I think that keeping air flowing over the cab is more about handling at high speeds... like in formula one, if you have more air going under the car, you can get some lift out of that... i don't think a prerunner style bumper with a skid plate would result in a loss of MPG... actually in some way you are decreasing your frontal wind resistance because you don't have that flat bumper pushing the air as much. with lifting trucks, you are losing the rake most of the time so it's harder for the air to move as smooth around the grille and cab.

i certainly could be off on this

Dirttracker18

That is the least of the reasons (if in fact any at all) for poor mpg of lifted trucks.

Bigger (read taller) area to push through the air, bigger tires (more weight and resistance to turning them).

Air moving under the truck has little if any effect on your mpg. No worries there. Your concern should be the difference in weight added to the front of the truck. Weight makes a far bigger difference in mpg and out trucks are a little heavy to start with.