im very dissapointed in the mileage im getting, i know i hotrodded it and everything, but still, i get 13mpg around town and highway, pulling 6k i get 10mpg, my truck has a 3 speed auto, 4x4, 3.07 gears, and 33inch tires plus all the performance stuff in my sig. why is my mileage so bad??? should i get that crappy of mileage?? thanks


jason

 

The auto sans overdrive is hurting you. The big tires are hurting your mileage and possibly the lift to some degree.

 

i guess i figured the larger tires would of helped highway cruising speeds, guess i was wrong, any other ideas, before this motor my 1st gen motor got 16 highway and 14 around town. anyone have any other thoughts???


jason

 

What kind of mileage do you expect to get with 445HP @ the pavement?? I have a mildly upgraded 300+ (underthehood ) hp rig and get a constant 21 driving back and forth to work. I don't think you can have that many horses and expect anything decent mileage wise. I think you can have one or the other (within reason) but both?? Oh sure, with your foot out of it but what fun would that be with a rig like yours???? But I agree with Mike.....ditch the 3 speed auto, along with those tires and you're off to a good start. That'll probably get you 4 or 5 more anyway. With a 5 speed (NV-4500) in there with that rearend you'd have a good Bonneville Salt Flats race truck that'd probably go 200 mph with that ratio....

 

Tall and narrow tires can give better highway mileage.
Tall and Wide kills it.

 

Ok stupid question time...... How does that work is it the rolling resitence?

 

Yep -- rolling resistance. You have more friction in the contact patch to overcome, plus more weight.

 

Put a 47RH in there with overdrive and lockup TCC - that should help - go to PATC for instructions with pics

 

darn i was hoping the mileage issue wouldn't be from the tries or lift, or the tranny, although i kinda figured the tranny was holding me back, so i thought taller tires would even things out, or not thanks for the help


jason

 

Yes. Wide tires have a larger footprint and run lower tire pressure for a given footprint. Hence, more rolling resistance and lower mpg.

Look at wheels designed for maximum efficiency: train wheels. Hard? check. Thin? check.

The closer your tires are to a train wheel, the lower the rolling resistance.

Taller tires will produce taller overall gearing, and reduce rpm to help mpg.

The best tire for mpg would be something like a 225 size 19.5 from Rickson. But that's just for hwy mpg-- in town you'd probably do worse because they are so heavy.

Justin

 

Have you corrected for speedo error from larger tires. If not, your getting better than you think...
http://www.sjdsm.com/tech/tire_size.htm

RJ

 

well to see if my speedo was off i drove 5 miles with my dad, me in my truck and him in his and his 5 miles were the same as mine, i noticed at his 5 mile mark i had only gone 4.8~9 miles so im only off by a hair. and actually before i lifted my truck i put these tires on and my mileage increased, with my old motor i got 16 around town with the taller tires i noticed i was getting more like 17-18 around town, but after i put the lift on my mileage dropped to a best of 14 around town and 15 highway. thanks


jason

 

Lifts hurt too, since they increase the frontal profile of the truck, increasing wind resistance. Not much, but you might be seeing something there, too.

 

im with chuxtruk, that amount of hp with that trans and lift with wide tires will do that to millage.

 

4.8 vs. 5 miles on your test...probably worth about 4%. Keep that in mind when your checking mileage #'s.