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Lifted my 15 Sierra today, already regretting it


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I lifted my 2015 Sierra today and now I'm wishing I hadn't. I'm new to this group because I just got my Sierra a week ago. I traded a 2003 Hummer H2 for my Sierra so I was used to 11mpg so when I saw 19-20mpg I was ecstatic. After the lift and the 35" tires now I'm seeing 13-14mpg. I knew the bigger tires would affect the mileage but I had no idea it would be this extreme. My truck has the 3.42 gear ratio. My stock tire is roughly 31.6 inches and the tires are 35 inches. Doing the math after the tire change the new ratio is roughly 3.09. According to a gear ratio calculator I would need 3.79 gears to bring the truck back to the original ratio of 3.42. 3.73 gears are as close as possible I can get to the 3.69 needed to return the truck to stock. My question is if I were to do this would my gas mileage return to what it was? I know going from a hummer that got 11 mpg I should be happy with the 13-15 but not when I was getting 19-20. Also would a cold air intake and exhaust help?

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Lifting the truck will affect the aerodynamics and cause a loss of MPG's and if you haven't recalibrated the speedo for the taller tire size that will also affect the MPG's and the shift points of the transmission. I used HPtuners to calibrate mine when I went with 33's and a leveling kit.

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I lifted my 2015 Sierra today and now I'm wishing I hadn't. I'm new to this group because I just got my Sierra a week ago. I traded a 2003 Hummer H2 for my Sierra so I was used to 11mpg so when I saw 19-20mpg I was ecstatic. After the lift and the 35" tires now I'm seeing 13-14mpg. I knew the bigger tires would affect the mileage but I had no idea it would be this extreme. My truck has the 3.42 gear ratio. My stock tire is roughly 31.6 inches and the tires are 35 inches. Doing the math after the tire change the new ratio is roughly 3.09. According to a gear ratio calculator I would need 3.79 gears to bring the truck back to the original ratio of 3.42. 3.73 gears are as close as possible I can get to the 3.69 needed to return the truck to stock. My question is if I were to do this would my gas mileage return to what it was? I know going from a hummer that got 11 mpg I should be happy with the 13-15 but not when I was getting 19-20. Also would a cold air intake and exhaust help?

If you re-geared your mileage would decrease further

 

 

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Regearing would help with mileage and low end power as will a tune. Exhaust and intake won't do much at all. When you lift a truck and put big heavy tires on, your mpg suffers, that's just fact and common sense.

 

 

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Here a major factor for you. What was the weight of the tire you took off? What is the weight of the tire you installed after the lift? I bet the new tires are at least 25lbs heavier each than the one you took off.

 

 

2014 Chevy silverado Z71 DCSB w/Bilstein 5100 level

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A friend of mine has a lifted Jeep Wrangler with 35" tires and something like 4.56 gears. He gets about 8 mpg around town and not much better on the highway. He always says, "With the big tires and lift kit, it's not about miles per gallon. You have to think in looks per mile".

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There is a lot of information available about the impact of wheel size and weight on MPG. You made a very significant change. Reducing your current tire size (and weight) will improve mpg and performance but you will lose the look you wanted. Spend some time researching this forum and you will find some very good looking trucks with more modest increases in wheel size.

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Remember, every pound of wheel/tire (unsprung weight) you add is equal to 5-7 pounds on weight in the truck, so if they are 25lbs heavier each you've effectively added 500-700lbs to your truck. Gears will help some but this is just how it goes when you do these things.

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