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Old 12-20-2015, 12:00 PM
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Miles per gallon

I'm thinking of putting a lift and bigger tires on my 2006 jeep grand Cherokee. It has a 3.7 v6 and I'm wondering what I can expect? I'm thinking of running a 255/75-17.

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Old 12-29-2015, 10:33 PM
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Re: Miles per gallon

I'd say a 2-3 MPG loss is reasonable.
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Old 01-30-2016, 01:11 AM
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Re: Miles per gallon

Did you end up going ahead with it?
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Old 01-30-2016, 04:39 AM
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Re: Miles per gallon

Yeah I have put a 2in lift and 255/75-17 tires. I'm getting about 12 to 12.5 miles per gallon city and maybe 15 hwy.
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Old 01-30-2016, 07:40 PM
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Re: Miles per gallon

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Originally Posted by jpen View Post
Yeah I have put a 2in lift and 255/75-17 tires. I'm getting about 12 to 12.5 miles per gallon city and maybe 15 hwy.
wow that's bad. id a figured you would gain a couple on the highway since the larger tire would in theory make the gearing taller, youd be turning less rpms
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Old 01-30-2016, 08:02 PM
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Re: Miles per gallon

I was hoping to be getting better than I am. It looks good with the bigger tires but they also scrub on the pinch weld.
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Old 01-30-2016, 08:08 PM
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Originally Posted by jpen View Post
I was hoping to be getting better than I am. It looks good with the bigger tires but they also scrub on the pinch weld.
Try a tuner like Hypertec. That may help with the mileage
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Old 01-30-2016, 08:11 PM
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Re: Miles per gallon

Thanks I will look into that.
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Old 02-09-2016, 08:54 AM
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Re: Miles per gallon

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Originally Posted by Strongjeff View Post
wow that's bad. id a figured you would gain a couple on the highway since the larger tire would in theory make the gearing taller, youd be turning less rpms
It doesn't actually work that way. While rotational speeds of the outer portion of the tire change, its not going to really have an impact on MPG the way you think.

In fact, larger tires have far more rolling resistance which make them very poor on gas mileage. That's why
economy cars tend to have such small and skinny tires.

Plus, when you lift a vehicle, the air resistance magnifies. A couple of inches can mean a loss of several miles per gallon.
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Old 02-09-2016, 09:04 AM
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Re: Miles per gallon

What are MPG's?

All I know is SPG. Smiles Per Gallon.

Plus with gas prices being at near historic lows, who cares.
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Old 02-09-2016, 11:45 AM
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Quote:
Originally Posted by NetworkTV View Post
It doesn't actually work that way. While rotational speeds of the outer portion of the tire change, its not going to really have an impact on MPG the way you think.

In fact, larger tires have far more rolling resistance which make them very poor on gas mileage. That's why
economy cars tend to have such small and skinny tires.

Plus, when you lift a vehicle, the air resistance magnifies. A couple of inches can mean a loss of several miles per gallon.
I'm well aware of how it works I was only focusing on the gear reduction from a larger diameter tire in relation to engine speeds
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Old 02-10-2016, 09:42 AM
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Re: Miles per gallon

Quote:
Originally Posted by Strongjeff View Post
I'm well aware of how it works I was only focusing on the gear reduction from a larger diameter tire in relation to engine speeds
The problem is, especially on these newer "whole lotta gears" transmissions, even that doesn't always work in a positive manner.

The result can actually be RPMs that are too low, which means going heavier on the gas pedal to try to maintain power. Essentially, you start lugging the engine, which results in the need to give it more gas to get the same acceleration, especially once you get to the higher gears where there's not a lot of power at all.
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