High RPM's on highway

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Bubbaprice

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Hello and thanks for the forums. I just joined the Dodge family with a 2008 Ram 1500, 4.7 l 2 door. I have only had her for about 6 months now, with spring here I'm staring to get out in the garage more and see what kind of maintenance she needs and what improvements I might want to consider.

Initially when I bought the truck it only had 70,000 miles on it and extremely clean. Dealer said the guy traded for a minivan because of a new family. The only things he seems to have done are audio, some lighting affects, larger tires, and exhaust. Other than that the truck seems to be stock.

Some of the things I have noticed but not sure if they are issues are that it only gets 13.3 mpg and most of my commute is highway. I have heard similar trucks getting 17. When I plug my OBDII reader it shows about 17 mpg average. But the price at the pump says otherwise.

My other issue is that while on the highway with cruise set. It will often downshift and be screaming at about 3k rpms. However if I give it just a little more throttle it will upshift and run at under 2k rpms. It is a constant adjustment to make, making the cruise kinda pointless. With very low hills it will downshift but on the downhill side it won't up shift back unless I give it more throttle. Then its fine again at 2k rpm.

I'm wondering if these two issues go hand in hand and have common reasons for happening?
Should the cruise be adjusting throttle more to help with shifting?

My other reason for posting is to ask what maintenance I should be looking at. I don't think the previous owner did much other than oil changes and I just now replaced the front shocks that really needed it. I actually have the owners manual and will be looking at it more closely. Having a third opinion will help decide what items I need to prioritize.
 

FCA Master

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Unless the computer has been programmed for the larger tires that is likely your problem.
 
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Bubbaprice

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The speedo is correct, would that still be an issue? Tires are just wider it seems 285/70-R17.
 
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tidefan1967

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For best fuel economy stay away from 10 ply mud tires and stick with the stock size and the least aggressive tread pattern you can find (the stock goodyears suck but they will get you good mileage) if you can afford it get a set of Michelin defenders in the stock size. I ran K02's on my previous ride and lost 2 MPG. The price for being cool is usually somehow intertwined with ****** gas mileage.
 

crash68

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,
The speedo is correct, would that still be an issue? Tires are just wider it seems 285/70-R17.
If the stock tire sizes l looked up were correct, the 285's on your Durango are approximately 2" larger than any of the stock sizes, upsized approximately 7% bigger (oem sizes: 245/70/17 265/65/17, 265/60/18)
Your stock size should be printed on the sticker in the door jam.
The 285 is the width, the 70 is a ratio, any time you change the width the height with change.
 
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