Jeep tire size upgrade and effects on mpgs?

I'll be needing to replace the tires on my Jeep in the near future. I'd really like to go with a taller/bigger tire, but I'm concerned about how it will effect gas mileage. I'm already not too impressed with the mileage I'm getting and making it worse certainly isn't a good idea. My normal yackin' around mileage is 16.something. I've hit 19.7 on a trip, but right now, on winter blend, with lots of morning idling I'm down to 15 and sometimes in the 14s. I really thought the XJ Cherokees would do better than most Mopar 4x4s of similar vintage.

Anyway, my current tire size is 235 65 R17. I've been unable to find specs on this size. I was using the tire section on Jegs site to get specs on 245s and other sizes. I'd just like to know what size I could jump up to without having an effect on mpgs. I also have to consider clearance issues. (I have a 3 inch lift.)

So based on what I already have, what do you think a good size would be for replacement tires?

Also, does a more aggressive tread design (think off road) vs. a regular street design have a negative impact on mileage? Any experiences?

my stock 97 avg'd 15. I used mud tires in 235/75 entire time I owned.

my 98 with 4in lift and 31's gets about the same. I will be regearing to 4.10's from 3.55's, so we'll see how that effects.

and I hear ya on the "it should get better".
I'm sure the "boxy" doesn't help.

My thoughts are that an all terrain tire ususally weighs more and "probably" has more rolling resistance.Two things that could negatively affect gas mileage.A wider tire may do the same.

Consider a narrower tire that is the same height or maybe shorter.Your lack of gear with a taller tire may actually hurt you as you are giving more throttle to move the vehicle.

Driving like an egg is under the gas pedal is the best way to improve gas mileage.

throw some 31X10.5's on it and move on....

Yes, those knobby off-road tires are good for nothing: Your mileage will be worse, they are noisy, need to be rotated all the time to keep from disintigrating, and they don't last very long. Yeah, if you really need to go off-road they help a bit..........help break stuff , by this time a person needs to get looking at an ATV to go "off-roading".

A 245, maybe even 265-70-17 should fill those wheel wells perfectly and you can get them in mileage-friendly tread designs. You may not even see any difference in mileage because these are still a fairly narrow tire.

It's when you go to the 31's mentioned or 285's and up that mileage will take a dump.

if mpg is your goal, keep the tires narrow and stick with a highway tread design. a little taller would be ok.

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throw some 31X10.5's on it and move on....

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