New Shoes, Crappy Mileage

Just got a set of 265/75/16 Cooper ATP's installed on my '12 DCSB 4.0L two weeks ago. I love the look, ride & handling, a huge improvement over stock. But my mileage is suffering. I used to get 20+ mpg avg but now I'm down to 16! I've even aired them up to 42/40 with no improvement. My driving habits have not changed nor the gas that I use. I installed new plugs 7K mi ago, so I don't think that's an issue either. I just can't believe my fuel economy would be reduced by 20%! Can anyone else chime in?

 

What load range are the tires?

 

Are those the exact same size as your original tires?

 

Welcome to the club.

 

They are standard load tires, original size were 245/75/16.

 

how did you not see that coming with more aggressive and larger tires?

 

I knew I would lose a little bit of mileage, but 20% seems extreme.

 

Now, now; he probably new there would be a loss, we all did, but I was getting 22MPG city driving before, and now I drive extra conservative on the highway and on a good tank get 18 mpg, but typically only 17.5 mpg. It is a pretty drastic drop.

 

Yes, it is, and I had a long debate when I just got new tires a few months ago because I wasn't sure if really wanted the look versus the savings. I still went with the bigger tires.

 

The ATP's aren't that aggressive either. They are very quiet on the road. I've had larger BFG AT's on two other trucks in the past and never had this kind of drastic difference.

 

Your tires are now ~3.7% larger than your previous tires...you must factor that into your calculations.

 

Maybe your calculating it wrong and forgetting to compensate that the larger tires have a longer rotation? tire size calculator

 

beat me to it lol

 

I run the exact same tire btw

 

The Cooper ATPs aren't an overly aggressive tire and, since they're still p-rated, shouldn't really be much heavier.

OP, drive with a lighter foot, especially on take offs and you should be able to get back to the 18 MPG range.

 

That's one of the reasons I chose them. I don't know how much lighter my foot can get though. Like I said, I was getting over 20 mpg avg, which is pretty good on our V6's. I use an UltraGauge to help maximize my mileage. On long hauls I've got 24+mpg in the past.

 

BINGO!!

Is the OP making the right calculations and/or has his Ultraguage setup properly?

Bigger tires means LESS miles/distance on the odometer.

 

did you set your ultra gauge to compensate for the larger tire size? (not sure if you can on an ultragauge, I have a scangauge)

 

Even factoring in the 3.7%, that would still make it just 16.6 mpg...

 

The UG doesn't have the option and with the larger tires my speedo and UG are actually accurate now. I checked with my GPS.