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I have a 2008 ram 2500 4x4 mega cab with 6.7 and a manual 6 speed. It was fully deleted, A&E air intake box and tube, 5" turbo back exhaust, with H&S Mini max, 305/55/20 tires when i bought it. I had seen upper teens and even low twentys for mpg. I have since put on a Banks Monster ram intake, Banks intercooler with all new bigger tubes, and went to stock size rims with 285/70/18 tires, put in a new Valiant dual clutch kit. And just recently had head redone and installed ARP head studs. Now I'm only getting 15-17 mpg tops. Any ideas why its getting worse MPG?
 

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hvac2448, are those hand calculated or from the evic? 15-17 mpg is pretty average considering cold season is here and of course driving habits comes in play. I doubt none of your recent upgrade would have affected it and with the factory wheels and tires it should have made it better. I'm currently getting 15-17 with a 35" tires..
 

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hvac2448, are those hand calculated or from the evic? 15-17 mpg is pretty average considering cold season is here and of course driving habits comes in play. I doubt none of your recent upgrade would have affected it and with the factory wheels and tires it should have made it better. I'm currently getting 15-17 with a 35" tires..
[/QUOTE
Thats hand calculated.
 

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You actually increased your tire diameter by a half inch so you should see a very slight reduction in RPM. You're moving more air so that will increase fuel consumption all things being equal, maybe turn that little 5 position switch down a notch??? Really hard to say without knowing how you drive, city or highway on the daily, all that good stuff. Change the intake elboy back off and see if the fuel mileage comes back. Other than that you may never know.
 

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Just because they are "upgrades" does not mean that things are going to improve, such as mileage & HP.
 

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Was the speedo ever adjusted for the larger tires? Is it correct now with the stock size?
 

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yea I don't see how those upgrades will do anything for or against MPG specifically. For the tires, what are the weights of the new tires vs old? the Rotational mass of the tires comes in big, arguably more so than the size. The new tires could be heavier. The Valiant dual clutch kit could come into play too, I don't know enough about them to say either way but I know they directly impact your power to the ground. Could be the fun factor dropping your MPG.

That said, it could just also be changes in the fuel and/or colder weather. I always seem to take a hit in the winter too.

15-17 is about right too btw.. make sure you are hand cacullating for many tanks. I tracked it with a sheet on my phone for over a year to determine my averages. I noticed the fuel type, brand, date, any changes I did to my tune, special out of normal driving or towing.. basically, I sit anywhere form 16-22mpg average. I finally just stoped, donn care any more.

Was the speedo ever adjusted for the larger tires? Is it correct now with the stock size?
^this... if your trip is off your hand calculations will be off too.
 
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