Jeep Enthusiast Forums banner

My tire size vs my mpg

3K views 43 replies 13 participants last post by  GreenbayTJ06 
#1 ·
I'm running a 2014 JKUR and have 285/70/17 tires, 2 inch spacer lift, and 4.10 gearing. Just recently figured out my actual gas mileage 14.3 miles per gallon city and hwy. Would bigger tires such as 35s help or decrease fuel mileage?
 
#2 ·
When on 35s (5.13:1 gears) I get 15.8@65 mph, 14.5@75 and 11.5@85 between sea level and 500ft flat hiway. This means one less stop for fuel on a 400 mile day so if I slow down to 65 avg speed I get there sooner than 75 avg!
Around town is nearer to 11 - my overall avg on 35s is 13.2.

On 33s my overall avg is 14.3 - I haven't speed studied yet as I have not had a chance to drive the long hiway stretch and haven't really averaged over 60 on the routes I have taken since putting on the 33s. But I am fairly certain the higher RPM will make a larger difference at the higher speed - best wild assed guess is closer to 15.0 at 65 and 10 at 85. The overall avg increase is most likely from requiring less effort to get to 45 around town (smaller tires make acceleration a bit easier on the throttle).
 
#4 ·
there are many variables too. like a 2door vrs a 4 door. The YEAR. city for some is going 35-40 never stopping. some its stop and go and at STOP your MPG is zero. auto or stick. the auto needs less gears for tire size today. Or 21= jks would need 5.13 gears just to turn 35s. But they do well with 35s and 4.1 auto. My 2d will light thetires in first on 35s 4.1 stock auto.

Truth is its a Jeep and MPG is not its intention. My old f250 20+ years 7.3 with almost 200K of towing miles can get 14 Towing the jeep on a trailer at 75. gets 18 no load.
 
#5 ·
Most of my driving is highway. In the city it's 30-40 mph with a stop now and then. I get jeeps were not designed to get any decent mpg but I hear of these guys on here with sports that have 3.21 gears and running 33s getting 18 a gallon. 18 would be nice
 
#6 ·
mine can get 18 mpg. its a 4.1 auto with 35s on steel rims. lift is 4.5+. Normal hwy though is more 17. in town can be from 14 -17. have the vic programmed with the correct tire Dia. tire?. But freeways heading out here are 75+ and at 80mph a Jeep is a flying brick mpg is more like 16 or less. right foot leads the way.

few things; most people run larger tires at lower psi too. That makes rolling resistance higher. So those beefing looking MTs wont roll as easy as what 27 psi max on a two door jk on 33 x12.5 + tire. when the factory roll at 37psi. 10 psi is a lot in the Hyper mill crowd.
 
#8 ·
Have you recalibrate the speedometer for the slightly taller tires? If not, that will throw off your actual MPG and make it lower than it really is. Won't be a huge difference with only a 285/70, but still a contributing factor.
 
#9 ·
Larger tires are heavier and require more to turn them. It's similar to carrying a load, so it will impact your mileage. However, unless your calculating your mileage the old fashioned way, you can't known for sure. If you're using the on board computer but have not recalibrated your speedo, then it won't be accurate. Buy a Procal or Superchips to recalibrate to your correct tire size. Not only will that help your on board computer correctly calculate your mileage, it will also tell your transmission the tire size so that it will be able to optimize your shifts, which can also help with your mileage.
 
#10 ·
Also, you said that you mostly drive highway, but how fast? If you're trying to run in the 75 mph range, then your mpg will suck! However, if you were to slow down to the 65 mph range, that will certainly help.
 
#13 ·
Wow, I don't really know what to tell you. You're certainly not going to get great mpg, but you should be getting a little better than 14-15 when driving at 70 mph. You can try dropping it to 65 mph and see what that does, and you can wave at the folks passing you. It's only 5 mph, so it won't make much difference with your travel time.
 
#16 ·
I didn't really think that the gas would make any real difference. Personally, I think you're wasting your money buying anything higher than 87 octane. Only a few vehicles actually require higher octane fuel, and some vehicles even give different HP ratings based on the type of fuel used. You're paying probably .25-.35 more per gallon for 91 octane, so you can do the math on 14.3 mpg.
 
#18 ·
2016 JKU 3.73/Trac-Lok, 6-spd, OEM 32" tires.

I almost never get below 18, usually 19.

I can break into the 20's on the highway in the 70's.

I've MANAGED 22-23 for 300-400 mile road trips on secondary roads mostly keeping it 55-65 mph.

Generally I can beat my wife's mpg in her V6 WK2 by a hair.

I chECK at every fill up. Old habit from motorcycles.
 
#26 ·
Maybe you all live where its flat with no wind, or maybe its all downhill with a tail wind..... Our Jk gets 15-16 with only 30" tires. Its an 08 6 speed.

Not going to get good mpg driving a brick at 70mph with 33" tires. Just isnt going to happen.
 
#30 ·
dont know about your 3.8 but my willys will easily pull 20+ on the highway with the stock 32s.
Maybe you all live where its flat with no wind, or maybe its all downhill with a tail wind..... Our Jk gets 15-16 with only 30" tires. Its an 08 6 speed.

Not going to get good mpg driving a brick at 70mph with 33" tires. Just isnt going to happen.
 
#32 ·
no envy no bragging. I didn't make my jeep so it sure isn't me that makes it get any better mileage. By the way mine has the air dam cut by the tires. I did the cheap bumper shortening thing. Didn't seem to effect my mileage a bit. The rest of the air dam is still there in place though. I think a lot of it revolves around the driver. I'm 60 years old and don't hot rod my jeep. I don't drive over 65 and rarely that fast. Mostly its kept under 60. If I want speed I drive my vette and when I want to haul stuff or tow things I use my truck.
 
#33 ·
my main point in that post is that I'm not the engineer that made the jeep. So why would it show favorably on me that mine gets 20mpg. It looks like a few others get the same so you cant really say I'm full of bs. Its fact not bragging. I don't even know you so what benefit to me would rubbing anything in your face be. Sorry pal but anyone that knows me will tell you that bragging or bs isn't the way I act.
 
#36 ·
Accepted (although sincerely not necessary). I am jovial and laughing 90% of the time. The time I am NOT - I am in meetings, at work under pressure or other tasks - but rarely on line.

We been here before brother! Lighten up and I'll TRY to post smiley faces more... :laugh2::grin2::wink2::laugh:

I am just now starting to slow down in my driving (54) - well except my Caddy - it begs for fast. But the Jeep is (as you experience) my slow ride... but still cant get it over 16 damn it...
 
#37 ·
I had the privilege of driving one of the new (well it was a 2015) supercharged caddys. It sure isn't you fathers cadilac! Thing would get right down the road!!!!!!!!!! Wish I could afford one but those days are gone.
 
#38 ·
Mine's the 14 VSport XTS (and I ordered it with a one off interior, the Platinum sand with delete the purple thread). It was my personal reward for running 20 years with a cost per mile below 45 cents on the company vehicles (very careful PMIs and holding 12 years avg on three vehicles rather than trading up). I drove the CTS V and VSport - the weight made a huge diff all around! But the trunk space is what decided. My wife's luggage leaves very little room for mine.
When I paid 48K for my 02 DHS it was like "unaffordable" but I DID hold it 12 and ran 257K miles on it. It replaced a 97 Lumina that cost me 18K - but with repairs over 150K miles, drove the cost over .70 per mile. Buying the higher quality build made it return more over my high mileage use. (I don't drive the high annual miles anymore - I have employees doing that now so the V hasn't even hit 15K yet). All told those 7 years with no note - the DHS cost me a total of .42 per mile excl fuel (and was a GREAT ride the entire time) and the average allowance on my tax return was .65! So I made enough money to "afford" the extra for the V package because repairing the Caddy was far cheaper than replacing the Lumina four times!
Not sure the run the wheels off strategy would work though if one drives less than 20K a year. Based on my wife's driving we would still be waiting to trade up a carburetor and 3 on the tree 68 Nova - she drives about 1200 a year at most! Obsolescence (remember the leaded gas die off of cars?) has to play into it somewhere...
 
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top