POBrien9

Hey guys, my 2008 3.8L is averaging 10.7 and sometimes worse. Every once a while it'll jump up to 12.Somethin on the interstate crusing at 60. I live in South FL where traffic is horrible but I don't see my MPG being this bad.. I'm running a 2.5 inch RC lift on 35 KM2s. Do you guys think there is a reason for these MPG? Thanks!

TXBeachJK

I average 13-14 mpg in my 2008 JKU with 33s. Could be any number of things causing the mpg... Gears, bumpers, hills, driving habits, traffic (as you mentioned), etc. 10 mpg does seem kinda low though.

pontiac31

Have you reprogrammed for the tire change? The larger tires will mess up the computer. I run 37" km2's and got just under 18mpg at 70 mph on a 275 mile trip this weekend.

TXBeachJK

Good point on reprogramming. Forgot to mention I used a flashpaq to reprogram mine. That probably will make a huge difference.

To the OP, you may also try to manually calculate mpg.

pontiac31

Manually calculated still would be difficult because the odometer will be incorrect also. You would have to calculate the difference in circumference and adjust it.

robsjeep9

Is that simply programming in 37" tires or more to it with that? I'm putting on 37's next mo and also have a flashpaq I haven't used in a couple years... Thx

skibovr6

I dont even get that with 35s pullin a trailer.

Gforce!

You should probably hand calculate your mileage, that just doesn't seem right. I don't have 35s, but I've towed a 2000lb boat on an 800 lb trailer and got 13...3 hours of driving each way

TXBeachJK

Correct. You would have to use GPS or other means of measuring distance. The odometer would be inaccurate.

TXBeachJK

If I recall, it's as simple as programming tire height (been a while since I programmed mine as well). You should be able to measure your tire to input the exact height. Ex. 34.5 or 35.5 for 35s for size variance.