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Old 09-18-2013, 08:42 AM
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MPG after new tires

I just replaced the bald stock tires on my 04 Grand Cherokee with 245/70r17 General Grabber AT2s and went from about 20mpg on highway to about 15.5mpg. Is this common or am I in need of a serious tuneup?
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Old 09-18-2013, 10:40 AM
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Re: MPG after new tires

The new tires are a bit wider then the stock ones, which will give some more resistance with the ground, but the mpg difference is too big. Did it really change directly after changing the tires?
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Old 09-18-2013, 10:43 AM
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Temperature got about 10 degrees colder outside. The tires are siped, maybe that adds a lot of resistance?
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Old 09-18-2013, 11:17 AM
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Re: MPG after new tires

Did you check your tire pressure after the temperature dropped?


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Old 09-18-2013, 11:37 AM
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No I haven't. They were installed when it was cooling off but they do feel loose. I'll check that out for sure! Any recommended PSI?
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Old 09-18-2013, 12:10 PM
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Re: MPG after new tires

I figure somewhere between what it says on the door jamb and the max indicated on the tire as a starting point.


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Old 09-18-2013, 12:17 PM
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Thank you for your help!
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Old 09-18-2013, 01:40 PM
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The door says 33 psi (cold)
The tire says 44 psi

They are inflated to about 35.5 psi each
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Old 09-18-2013, 01:49 PM
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Re: MPG after new tires

Quote:
Originally Posted by Bnesja View Post
The door says 33 psi (cold)
The tire says 44 psi

They are inflated to about 35.5 psi each
35.5 cold or hot?
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Old 09-18-2013, 01:52 PM
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Cold. It's been sitting out in the parking lot all day.
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Old 09-18-2013, 02:39 PM
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Re: MPG after new tires

That doesn't sound bad. You might try adding a couple of pounds if it doesn't adversely affect the ride.


And do that tune-up for good measure.


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Old 09-18-2013, 02:40 PM
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Thank you for all of your help.
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