Mileage drop

achacon

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Factory setup I was getting right at 19 mpg. 4" lift with 35's and my mileage dropped to 12mpg. A friend of mine has the identical truck and his mileage dropped to 15mpg. I was expecting a drop to 15mpg but not 12mpg. Anyone else have a severe drop in mileage going to 35's?


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griz700rocket

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Depends more on the weight of the tire than the size. I believe this is why people see different results after changing tire sizes.
 

ckrueg

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There's a few factors that will contribute to this. Increased mass as well as tire diameter will increase the torque required to accelerate. More rolling resistance also will reduce efficiency, and rpm changes due to larger tires can also reduce efficiency from lugging the engine too much or being in a lower gear right before a shift.

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CATDiezel

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The lift is on upside down. Happens all the time. Turn it over and you should see 26mpg.
 

Justus

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Yes, I leveled the front and put on the tires in my sig and went from 18-19ish to 14 ish. And yes I was very disappointed, I thought 1-2, but not 4-5. Oh well, I love my tires.
 
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Floorboard79

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going to "35's" from my stock "33's" i lost about 1 mpg, but stock i never could get more than 17.xx driving normal. CCLB lariat 4x4 stock suspension and wheels. your initial figure sounds off, my boss went from about 16.5-17 to 14.5-15 in his 2014 going to a 4" lift and 35's. did you re-calibrate speedo, what size tires were stock
 

Justus

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I think I have tuned it right. I have the SCT X4 and I set it to 570rpms per mile, which 35"s run 576 right? Then when it asked me if I changed tire size the only options started at 600 and went higher from there.

I think I did it right, please tell me if I am off so I can correct it. Thanks
 

achacon

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You can't recal the speedo on the 17's. Plus factory tires are 34's and going to 35's wouldn't make a noticeable difference in the speedometer. I've owned all three brands and this is my first ford. Never had this big of a drop in mileage. Luck of the draw I suppose


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Floorboard79

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You can't recal the speedo on the 17's. Plus factory tires are 34's and going to 35's wouldn't make a noticeable difference in the speedometer. I've owned all three brands and this is my first ford. Never had this big of a drop in mileage. Luck of the draw I suppose


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if you have 17" or 18" wheels the tires are smaller than the 20's. You can re-calibrate the speedo with forscan, once you go past a small amount of correction it trips a DTC.

My stock tires were 275-70-18, put 285-75-18's and got it within 1% correct with forscan and no DTC in a few thousand miles. When i went too far it tripped a DTC

I think hypertech makes a speedo deal too
 

lincolnlocker

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if you have 17" or 18" wheels the tires are smaller than the 20's. You can re-calibrate the speedo with forscan, once you go past a small amount of correction it trips a DTC.

My stock tires were 275-70-18, put 285-75-18's and got it within 1% correct with forscan and no DTC in a few thousand miles. When i went too far it tripped a DTC

I think hypertech makes a speedo deal too

I have 18s with 305/70s(35-12.5r18) and my sct has my mph dead on with my garmin gps..

I might have lost 1mpg... if that.. im still getting high teens for mpg on the interstate. 20ish if I set cruise at speed limit

mine is a 12 though.. not a 17..

live life full throttle

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Justus

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Anyone have input on this?

I think I have tuned it right. I have the SCT X4 and I set it to 570rpms per mile, which 35"s run 576 right? Then when it asked me if I changed tire size the only options started at 600 and went higher from there.

I think I did it right, please tell me if I am off so I can correct it. Thanks
 

highdrum

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if you have 17" or 18" wheels the tires are smaller than the 20's. You can re-calibrate the speedo with forscan, once you go past a small amount of correction it trips a DTC.

My stock tires were 275-70-18, put 285-75-18's and got it within 1% correct with forscan and no DTC in a few thousand miles. When i went too far it tripped a DTC

I think hypertech makes a speedo deal too

What forscan code did you use? I went from 275/70R18 to 295/65R20 35.1" your 285/75R18 is 34.8". I have tried a few different codes and always get the DTC for transxale ratio being off.
 
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