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Discussion Starter #1
alright i have a bone stock bdy/tire wize sd, i get about 17mpg hwy going 65 mph. now i want to put a leveling kit on it with 35" tires, now my gears are 4.10 so i figured the taller tire would lower the rpms enough to offset the heavier wieght and more rolling resistance of the bigger tire? am i way off here thinking this, by the way the tire i am lookin at getting is the 35x12.5 bfg all terrain.
 

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I can get 17-18mpg with a 4" lift and 35'' bfg's, 3.73 gears, 6spd, thats if I drive very consevatively and go about 60-65mpg usually, but thats mostly only smaller local hwys. At 70 mph I think my rpms are around 1925 or so, I cant remember what they were at 60. With the way I usually drive, I get a pretty easy 15 or so out of it, but that is also with short trips that only halfway to work i'm just getting to op temps.
Hope this helps.
 

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Expect to lose 2 MPG when you put the big tires on it.
 

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Discussion Starter #4
so would you sugjest a 33x10.50 i mean right now my rpms are to high at hyw speeds to get any decent mileage, only way to get my mpg above 18 is to stay under 65, i want to be able to go 70 and still see the mpg. mabey some cookie cutter 33s?
 

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i get about 16ish at 65 on 35s.
 

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Discussion Starter #6
by the way what did you do to your truck engine wize to pull 27 mpg? i see you have it lowered and airdamed/bedcovered but what did you to to the engine? im guessin tuner but who did you use? thanks, also what do you think about me lowerin my 4x4 and throwin some 3.08s in it?
 

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Most of Dave's stuff is aerodynamics, gearing, and most importantly driving habits.
I went up to 285/75's, Which are basically 33's, with a much more aggressive tread, and I lost 1.8 mpg. I've gained 1.6 of that back by even more conservative driving.
 

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Discussion Starter #9
yep mine are exactly the same as yours , i have 31.2 inch tall tires (measured with a tape) thats how i figured i have 4.10 gears.
 

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I know the OBS is a little diff. But i lost about 2MPG with the 35" tire 4.10s
 

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Jay:

The only thing I've done to the engine has been a 203 degree thermostat. These engines are pretty well sorted out as far as MPG goes. I haven't seen anything that makes any huge difference. Single-shots did not help my MPG. Chips and tuners haver been neutral at best.

I don't think you can lower a 4x4. The numerically lowest R&P sets you can get for the front axles are 3.55:1. Now that Ford makes them standard on new Super Duties they should be easy to find.

I do recommend getting a pyrometer. Drive to keep EGT below 600. It will take a while to get the knack but it can be done even with an automatic.

Driving is the cheapest and most effective mod you can do. Read http://www.cleanmpg.com/forums/showthread.php?t=1510

This guy is the guru - his politics notwithstanding. Some of this stuff is hybrid specific and some of it you ca't/won't wouldn't on a bet do. Pick out what you can do and integrate it into your driving.

A fairly cheap mod that works is a tonneau cover. Good for 1.5 MPG and a quieter road ride.

Stay with the tires you have. Unless you burn up the Interstates 12 hours a day, acceleration from stops will eat you up if you get bigger tires.
 

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when i went from 285's to 315's i didnt see any difference in MPG... its all about how you drive it. I get around 16... thats mixed country city driving
 

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Discussion Starter #13
I been driving while watching the pyrometer and keepin it under 600, now i just filled up and calculated my mpg for the last 400 miles of mixed city/hyw but mostly city and i got 17.8 mpg thats pretty good even if i do feel like a grandma drivin around town. im goin outof town next week and will get to see what the mpgs are with the php tuner on fuel sipper setting and driving with the egts under 600 ill let you know what it comes out with.
 

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255/85/R16's I could regularly achieve 21-23mpg with this size tire on my 97 when it was stock height. With my lift and 35's I usually see 17-19. I can still get in the low 20's if I really baby it and stay under 65.


Dave
 

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255/85/R16's I could regularly achieve 21-23mpg with this size tire on my 97 when it was stock height. With my lift and 35's I usually see 17-19. I can still get in the low 20's if I really baby it and stay under 65.


Dave

what gears are you running to get that mpg???
 

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Discussion Starter #18
alright i just got my mileage calculated again when i filled up 2 days ago. I drove 405 miles on this tank of gas when i filled up i squeezed 21.1 gallons to the brim. So i averaged 19.1 mpg. i still dont have the php in yet but this next tank of fuel will be with the php on fuelsipper. I do have the stage one single shots in and that is what i got this 19.1 mpg with. The idle is all weird because im still running the stock pcm set up for split shots so im hopin with the tuner set up to run on single shots it will be even better. BTW this was mostly hwy going 65 mph most the time and about 100 miles of city driving. I am still thinkin about going to a 4 inch lift and 35s just so i can do a little more driving offroad. If it makes my mpg go down dramaticly i will just sell it all and go back to stock.
 

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Been dribing back and forth from Denver almost every day for the last week and i've been keeping a close eye on my mpg. This driving from Denver elevation about 5500ft(give or take) up to about 11,500 ft elevation and back down to 8500 ft elevation where I live now. I haven't been babying it at all, i've been averaging right at 19mpg and today when I filled up it came out to 19.4 mpg. Not bad for my big ol truck and haulin butt up all them long grades...


Dave
 

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For me it depends on the traffic but i usually get 14-16mpg and the best ive ever gotten was 22mpg lol thats with 35''s
 
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