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Hey All -

So over time, mainly in the last 2 months I have been getting 9-10MPG around town and on the highway it was about 12MPG. It used to be 22 and 15MPG.

I installed a Volant CAI, Magnaflow/Muflex 18 and I have 2" level and 35" Nitto Trail Grapplers and a catch can if that matters at all.

What is the deal? This is crazy. Could my oxygen sensor be screwed up, do I need to tune the engine to the new tires?

Any suggestions would be awesome.
 

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That seems about right to me...maybe a little low, you could probably get 10-12 in the city if you keep your foot out of it
The Hemi begs to be played with an we all do it
Your 2 inch level and 35's have taken away the aerodynamic effects of the truck, hence the bad MPG
 

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Was thinking the same thing. Higher you go, less the gas mileage will be.
 

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Were you getting the higher mpg's before or after you installed the mods? I'm willing to bet its mostly due to the lift and tires, however, it still sounds a little low
 

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Sounds a little low to me but in the lift research I've done your numbers are about right. Higher the truck with larger tires takes more fuel to push around.
 

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Ya thats about what they get with big 35s and level installed.
Remember that the speedo/mpg computer will be off about 10% now with the bigger tires aswell so compensate for that
 

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Could be a gearing issue as well. What size gears do you have? Your truck has to work harder to push all that extra rotational mass that you added on each corner to get it going.
 

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Did you recalibrate you speedometer for the bigger tires? If not the computer thinks you have driven less miles than you actually have so it will read out a lower mpg.
 

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My 2500 hemi lost 2-3mpg when I went from 32" to 34" tires. City mpg went from 14 to 11-12. Hwy went from 19 to17. I added an AFE intake and got about .5-1 mpg back. I drive like Granny Bluehair 95% of the time, rarely above 2500 rpm.

Side note, if anyone has a nice set of name brand 265/70r17 all terrains with less than 3k on them and is up for a trade of some 295/70r17 Toyo MT with less than 3k, I might trade you. I'd like my mpg back.
 

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Oh and to the OP, my GPS shows that the odometer is off quite a bit. GPS shows 1.16 miles for every 1 mile on the odometer. The speedometer shows 66 while GPS shows 70.
 

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you need to have the dealer flash the ecm so it "knows" you put some larger tires on it. you will then be able to calc. your mpg with corrected numbers. you will find you lost some mpg, but not near as much as you think. i would do this before i traded out my tires.
 
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