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Discussion Starter #1
2007-2008 6.7L 4X4 owners: I'm getting 17+ mpg around town, almost 20 on the highway. I've been told this will increase somewhat as the cummins breaks in, maybe up to 22 on the highway.

I'm going to mount either 295, 305, or 315's on my 2008, wondering how everyone's mileage is with any of these oversize tires.
 

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Is that hand calculated?????? Most people bone stock are seeing 12-13. With MP-8 or some form of chip some are seeing 15, 16, 17. Again with the DPF delete gaining even more mpg's. Tires size will kill that in a hurry!!!

I have run about 3000k miles on my DPF delete kit and MP-8. I have been averaging 18 mpg. With 305/45-22's (about 33x12.5)
 

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Those can't be hand calc'ed numbers unless you somehow drive downhill wherever you go. :) I lost about 1-1.5 mpg off my hand calc'ed numbers when I went from the stock tires to 315/70 17s. The loss is about the same with the true 35" Toyos I'm running now.
 

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I'd do anything to have that kind of mileage!! My 08 Mega Long has never seen over 13MPG. Mostly it would get 11 MPG. empty!! I took my 19.5's off and now am in the upper 12's. My steel 19.5's were 33-1/2" tall with the 245 tires. They ate 1-1/2 mpg average.
 

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Not a 6.7 ,but a 5.9 & I lost about 1 1/2-2 mpg when I went to 35's Toyo's.
 

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Discussion Starter #7
The numbers I'm reporting (17/20) are the ones calculated by the overhead console electronics in my 2008. My truck is bone stock running 265/70/17's and I don't have a lead foot. Yet.

Maybe I should start hand calculating my mileage??

Anyhow, thanks for the replies so far. I'm sure I should expect 1-2 mpg loss if I increase a tire size or so.
 

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Just curious to the guys that lost mpg with larger tires, did you correct for tire size? On my wifes truck she never remembers and when I tell her that because of the larger tire size she if off 10% I see a light :). If you are not correcting for the tire size on the speedo then maybe you are not actually losing any, maybe a little? Just a question
 

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Just curious to the guys that lost mpg with larger tires, did you correct for tire size? On my wifes truck she never remembers and when I tell her that because of the larger tire size she if off 10% I see a light :). If you are not correcting for the tire size on the speedo then maybe you are not actually losing any, maybe a little? Just a question

I hand calculte mine with the different size tire figured in. I lost about 2 mpg with the toyo M/T's. Running 315 BFG A/T's for summer & I lose about 1-1 1/2 mpg.
 

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Hand calculated i get about 19 on the highway and 14 around town
 

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my truck got 22 mpg on the way home from the dealership(trip 150 miles) gone down eversince. I was told that same crap, it will get even better once it breaks in. The over head now stays around 13 in city and up to 17 hwy. Mine is also a straight drive which is suppose to be better. I wouln't look forward to any better milage. 6.7 nice power but milage SUCKS and fuel here $4.19 a gallon.
 

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Discussion Starter #12
Thanks biggyb1. I'm wondering if you've calculated your mileage or just read it off the overhead. I'll probably start calculating mine with every fillup and comparing it to what the truck tells me, if I don't pass out from the price at the pump. It's $4.24/gallon here...
 

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A friend of mine has an 07 mega 4X4 6.7 2" leveling kit,juice w/attitude 35"x20"X9" Toyo Open Country M/T , 6-Speed Man Trans w/ 3.73 gears averages 700-750miles per tank on highway going from here Cuero, Tx to Lake Charles, La around town for a week and back home with no fueling in between!!!
 

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I run 305/70/17 nitto terra grapplers on my 08 mega cab and I have 5500 miles on it. I only get 12 to 12.5 empty and 8 to 8.5 pulling my 24ft gooseneck. These are hand calculated numbers.
 

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I have 315/70/17s on mine with egr on and exhaust gone i was at about 15.5 hand caculated with egr gone and exhaust gone im at 17.8 hand caculated
 

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i lost about 3 mpg with my 37's, and that is with the speedo corrected.
 

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13-16 mpg, diesel at $4.40 a gal. and still running 37s. Only in America! :coocoo
You got 3.73 or 4.10 gears? How's the power?
 
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