Offroad Tires and MPGs

[sp3ct3r]

For those of you who have all terrain tires, did you experience any loss in fuel mileage compared to "normal" tires?

 

[WICKED KJ]

31x11.50x15's, 10.3 mpgs

 

[snowsport]

It depends on the size. If you choose a tire size close to original, then an all-terrain tire usually doesn't harm mileage much. The bigger you go, the more effect it's going to have, unless you regear your diffs. Also, depends on things like side wall thickness (weight of the tire), which can vary from one tire to another of the same size.

 

[kj924]

I installed 245 75 16 BFG AT's with my 3" lift and I dropped about3 mpg. Now the at's are load range E, so they are a heavier tire than average.Oh and my Moabs are a bit heavier than the stockers too.

 

[J-Thompson]

tire OD changes your over all gearing
thus it changes how hard the engine has to work to go and maintain speed

a good example of this would be looking at say a 31 X 11.5 Super swamper LTB
the weigh in at 50+# each
then look at the BFG KM2 in a 33 X 10.5 weighing in at 55# each
I can not run the BFG on my TJ due to gearing
well I could but I would not be happy off road
but the difference is only 5# per tire
the OD is what is killing you and it will cause poor MPG and loss of power
yes weight and tread do account for some of the loss but I would say less than 25%

WICKED KJ
if you are only getting 10 mpg's then you have something else wrong or you have 3.55's
I have the same ,if you have LTB's, tires on my TJ with a 3 speed auto and 3.73
with lots of weight (over 4600# with out me in it) ,sliders ,skids and a bunch of gear and I still get 15+ with a very inefficient I6
oh and I am cranking out 3000 rpm to do 70 mph

 

[J-Thompson]

oh and by the way AT's are not "off road" tires
Super Swampers are an off road tire
why?
because AT's are great on road and Swampers SUCK on road
reverse it for off road
why?
because you simply can not have both

 

[tjkj2002]

tire OD changes your over all gearing
thus it changes how hard the engine has to work to go and maintain speed

a good example of this would be looking at say a 31 X 11.5 Super swamper LTB
the weigh in at 50+# each
then look at the BFG KM2 in a 33 X 10.5 weighing in at 55# each
I can not run the BFG on my TJ due to gearing
well I could but I would not be happy off road
but the difference is only 5# per tire
the OD is what is killing you and it will cause poor MPG and loss of power
yes weight and tread do account for some of the loss but I would say less than 25%

WICKED KJ
if you are only getting 10 mpg's then you have something else wrong or you have 3.55's
I have the same ,if you have LTB's, tires on my TJ with a 3 speed auto and 3.73
with lots of weight (over 4600# with out me in it) ,sliders ,skids and a bunch of gear and I still get 15+ with a very inefficient I6
oh and I am cranking out 3000 rpm to do 70 mph

I get 10mpg's for city driving,though here in CO you are always going up hill(it seems) and starting from a stoplight with 5500lbs going up hill is a mpg killer.On the open road I can get 20+mpg's,went to Greeley Co last week(250mile round trip) and averaged 21.2mpg's.I'm also running 265/75R16 Interco Trxus MT's(31.9" tall) on 16x7 steelies(90lbs total each) and have 4.10's,though the 4.10's are not near enough gearing for 32" tires but the lowest a KJ can go.The 5.13 gears I'm going to soon with 35" tires should gain me mpg's for city driving(thinking about 18-20mpg's in town).

 

[Ry' N Jen]

I get 10mpg's for city driving,though here in CO you are always going up hill(it seems) and starting from a stoplight with 5500lbs going up hill is a mpg killer.On the open road I can get 20+mpg's,went to Greeley Co last week(250mile round trip) and averaged 21.2mpg's.I'm also running 265/75R16 Interco Trxus MT's(31.9" tall) on 16x7 steelies(90lbs total each) and have 4.10's,though the 4.10's are not near enough gearing for 32" tires but the lowest a KJ can go.The 5.13 gears I'm going to soon with 35" tires should gain me mpg's for city driving(thinking about 18-20mpg's in town).

That's what I'm thinking about with a tire size of 245-70 or 75-16 is the drop in mileage. Every bit helps with gasoline at .91¢ per liter.

 

[jsc7002]

I have 245/75 on steel wheels and I average about 14mpg all around

 

[Ry' N Jen]

I have 245/75 on steel wheels and I average about 14mpg all around

That's pretty decent.

 

[jsc7002]

it's not terrible but I am still trying to re-gear it to get it back up and gain some power

 

[Dave]

I didn't notice any difference in gas mileage when I took the stock Goodyear HP's off and put on AT's in the same size. I thought I was going to lose gas mileage at the time so I was checking it. The Goodyears just didn't do anything "good".

But as was said previously, AT's are not off-road tires. They are a compromise.

Dave

 

[tommudd]

I done mine in baby steps so haven't noticed that much change went from stock 235-70s, then 245-70s, next 255-70s, and now 265-70s still get 19/20 easy at 75 plus on the road though!

 

[sleeve]

I believe there are a couple factors that will determine what loss (or gain) in MPG you and your KJ will see.

#1) Jason is right on about the tire size.. When you go up in size, it takes more gas to get the KJ moving. Which in turn lowers your MPG

#2) The Tire weight. I believe that Jason also mentioned this, but if your stock tire weighs in at 45lbs and your new tire weighs in at 50lbs than you will notice a small drop in fuel economy.

#3) Tread. While not a huge factor, a tire that has soft sticky tread will have a higher rolling resistance than a tire with harder [highway grade] rubber.

#4) Changes in tire pressure


In my case, I went from Goodyear RS-A's to the Firestone Destination A/T's while staying with the stock tire size of 235/70/16. The change in rubber resulted in a .1MPG drop in gas economy over the last 2 years. So it's possible to retain your "MPG" rating on the KJ but there are a lot of factors to look at when trying to determine the impacts.

Also, the KJ is not good on gas anyway so...

 

[sp3ct3r]

I believe there are a couple factors that will determine what loss (or gain) in MPG you and your KJ will see.

#1) Jason is right on about the tire size.. When you go up in size, it takes more gas to get the KJ moving. Which in turn lowers your MPG

#2) The Tire weight. I believe that Jason also mentioned this, but if your stock tire weighs in at 45lbs and your new tire weighs in at 50lbs than you will notice a small drop in fuel economy.

#3) Tread. While not a huge factor, a tire that has soft sticky tread will have a higher rolling resistance than a tire with harder [highway grade] rubber.

#4) Changes in tire pressure


In my case, I went from Goodyear RS-A's to the Firestone Destination A/T's while staying with the stock tire size of 235/70/16. The change in rubber resulted in a .1MPG drop in gas economy over the last 2 years. So it's possible to retain your "MPG" rating on the KJ but there are a lot of factors to look at when trying to determine the impacts.

Also, the KJ is not good on gas anyway so...

AH, I see
Well that's good. I plan on getting some Destination A/T's too whenever I change.

 

[offrovering]

if you are staying close to oe spec you won't even notice.

I can't believe some get 10mpg. Something doesn't seem right, not with this type of vehicle, unless that gearing is way off, and if it was I would be worried about other things than mpg.

 

[tjkj2002]

if you are staying close to oe spec you won't even notice.

I can't believe some get 10mpg. Something doesn't seem right, not with this type of vehicle, unless that gearing is way off, and if it was I would be worried about other things than mpg.

Add 1500lbs to your KJ,run tires that you can not gear correctly for and see what your MPG's are.

I get 10mpg's in town and can get 21mpg's on the highway,sitting at 5500lbs(4000lbs stock),31.9" tall tires that weigh 90lbs with the rims and need 4.56 gears to get back into OEM powerband(taking the vehicle weight and tire weight into account,4.27's would be the paper gear ratio).Oh and did I mention that I live at 6000'+ altitude,and of course my KJ is in perfect running condition,better then about 90% of any vehicle running today.

 

[JeepJeepster]

I get 12mpg pure city. My Jeep isnt much different then a stock kj with the offroad package other than the 3" lift and 245/70 tires. Kinda hard to get 18mpg at 75mph but we have lots of hills and rolling hills around here.

 

[tjkj2002]

I get 12mpg pure city. My Jeep isnt much different then a stock kj with the offroad package other than the 3" lift and 245/70 tires. Kinda hard to get 18mpg at 75mph but we have lots of hills and rolling hills around here.

That's odd that I can pull 21mpgs on the highway here in CO and we have mountains,and big ones.

 

[offrovering]

Add 1500lbs to your KJ,run tires that you can not gear correctly for and see what your MPG's are.

I get 10mpg's in town and can get 21mpg's on the highway,sitting at 5500lbs(4000lbs stock),31.9" tall tires that weigh 90lbs with the rims and need 4.56 gears to get back into OEM powerband(taking the vehicle weight and tire weight into account,4.27's would be the paper gear ratio).Oh and did I mention that I live at 6000'+ altitude,and of course my KJ is in perfect running condition,better then about 90% of any vehicle running today.

what size tires?

1500 extra lbs?