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I have a 2012 dually with deletes and h&s. I now have 285/12.50 tires on it. I'm just needing help on how to get the best fuel mileage I did calibrate the tuner for the bigger tires but would some type of custom tune do better? Probly lost 2 miles a gallon when I put the bigger tires on it. I leave the tuner on hot when not loaded(drive like grandma). I change it to mild setting when towing. Any ideas? Just drove 1,000 miles to south Texas with bumper pull trailer with hardly any weight on it and was getting 10 mpg



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I have a 2012 dually with deletes and h&s. I now have 285/12.50 tires on it. I'm just needing help on how to get the best fuel mileage I did calibrate the tuner for the bigger tires but would some type of custom tune do better? Probly lost 2 miles a gallon when I put the bigger tires on it. I leave the tuner on hot when not loaded(drive like grandma). I change it to mild setting when towing. Any ideas? Just drove 1,000 miles to south Texas with bumper pull trailer with hardly any weight on it and was getting 10 mpg



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When I changed tires on my truck the H&S tire calibrator was way off. I had to use a gps and do it manually with the programmer.

Bigger heavier tires does not equal better gas mileage, why did you go bigger if you were worried about 2MPG?
 

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I have a 2012 dually with deletes and h&s. I now have 285/12.50 tires on it. I'm just needing help on how to get the best fuel mileage I did calibrate the tuner for the bigger tires but would some type of custom tune do better? Probly lost 2 miles a gallon when I put the bigger tires on it. I leave the tuner on hot when not loaded(drive like grandma). I change it to mild setting when towing. Any ideas? Just drove 1,000 miles to south Texas with bumper pull trailer with hardly any weight on it and was getting 10 mpg
Assuming you are running an H&S tuner (mentioned "hot")... I would update the tuner so you have the newer calibrations with the better timing maps... then re-load your tune and select "3" for timing.

Though custom tuning can yield better MPG, there is no guarantee due to all the variables that create your MPG.

Lifted 3500 4x4 with big tires and heavy wheels... triple threat to your MPG :(
 

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When I changed tires on my truck the H&S tire calibrator was way off. I had to use a gps and do it manually with the programmer.
I had the same problem, the H&S wasn't even close but eventually figured out which size to change it to.
 

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You might try custom MCC tuning by Draconian diesel. Also when you recalibrate for the tires you cannot use the tire manufacture size. I am on my second set of 285/75/17 Terra Grapplers and love them. The manufacture size is 34", but you have to measure the actual ties with a yard stick. They measure at 33" and that is what I put in the tuner and my speedo is spot on. Still getting 20 mpg hand calc highway at <70 mph.
 
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