Bad Mileage with 33" Tires

[GladiatorNate]

I'm new to Jeeps and aftermarket wheels and tires, so I'm wondering if anyone could help provide some insight with my situation.

I have an Overland that I bought with 18" aftermarket Krank Offroad wheels and 33x12.5 General Grabber x3 tires. I was usually averaging 16 mpg, and could get 18-20mpg on the highway. Not great, but it's a Jeep with heavy tires, so oh well.

I recently had the steering gear TSB service completed, and the 1.5" Teraflex front leveling kit installed at the same time. When I received the Jeep back, the average mpg was reading 13.2. I've since installed a Tazer to confirm the tire size is correct. With mostly city driving, and not being heavy footed on the expressway, I'm still only getting an average of 13.6 mpg.

Any thoughts on what could have caused the change? Would that have happened because of the leveling kit? The dealership says the mpg change is due to the winter weather here in Michigan.


Other info:
- Automatic transmission
- Mostly city driving, short 10-20 min drives on the expressway
- 8,000 miles on the truck
- 3.73 gears
- Can only see 18 mpg when going downhill on the expressway at 70 mph in 8th gear, usually it's closer to 15mpg.

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[LostWoods]

You have 3.73 gears, went 3" larger on the tires, and picked some of heaviest 33s available which have 80% of their mass in the tread. Essentially, you almost doubled your rotating mass, the added weight is all in the worst possible place, and you pushed that worst possible place further outward. You're going to take a huge hit any time you need to get that weight moving which is why you're seeing terrible city mileage and you have an aggressive tread that is hurting your freeway MPG.

The solution is smaller, more road-friendly tires and the band-aid is re-gearing to the 4.56 range.

 

[Ghostwave]

Dealer put on bigger tires and didn’t re-gear. No idea why it got worse, typically engines love the cold air, so that’s opposite of my experience and understanding. Small changes in vehicle orientation can have big changes in aerodynamics, but since it started as a brick and finished as a brick, wouldn’t have guessed it would make a big difference. But typically those things need measurements more than guesses.

In any case, the gearing may still be the big Knob to turn before any of the other little knobs. Weird.

 

[LostWoods]

Engines love the cold air but not winter gas. A 10-15% drop in MPG is common.

 

[MrZappo]

This is simple:

Bigger Tires
MUCH Heavier tires (Are you running proper pressures ?)
MUCH more aggressive tread
3.73 Gears (not great for higher loads or harder to turn wheels/tires)
Lifted (Less aerodynamic)
Longer engine warm up times due to outside air temp.

I can tell you that that gear ratio is way low for 33 inch tires ... My Mojave came stock with 4.10 and at speed it is a DOG ... I cant imagine being on 3.73 !!!

That gear ratio is only useful IMHO for small highway oriented tires ...

 

[Jeeperjamie]

4.10 gears and you will be back to where you were at. I got 4.10 gears on my Sport Max Tow Nd I get 18.5-19 average and a little over 20 on longer trips and that's on 35's riding as seen in the picture

 

[unsocbl]

I run Falken Wildpeak 33" (255/80-17") at about 46lbs each on 3.73's. My mileage didn't noticably drop, Average 21 mostly highway/city.
I added a Rancho leveling kit and really no noticable drop.
Winter hit, I'm down to about 18mpg...so mostly going to be the fuel blend for winter.

If you want a bit better mileage and performance, look for a lighter tire.

 

[TrainMan]

I was getting almost 16mpg during the summer and fall. Now it's January and I'm getting about 14mpg. I blame winter gas. Lifted, 35s with 4.10.

 

[GladiatorNate]

Thanks everyone! I figured it was a combination of all of the above, just wanted to make sure nothing was "wrong" and in need of repair.

Tire pressure is at 36psi, would you recommend differently?


These tires came on the truck when I bought it, I didn't realize they were almost twice the weight of the stock tires - ouch. When these wear out, I'll look into lighter options.

I also didn't really think about the longer idle times in the winter, but remote start does get used often.

I guess I just didn't think that I would lose ~3 mpg because of all this, but you live and learn. Good thing I didn't buy a Jeep for good gas mileage

 

[Ohio JKU]

As bad as the mpg might be, don’t forget to include the price of tires, and it’s only the difference in mpg loss that calculates.... so depending on how much you drive/difference = cost of new lighter tires...

 

[Blade1668]

My MPG has been all over since "winter started" but not to my norm here so a part is probably the fuel and weather. Rolling resistance and weight of tires rims in stop and go driving then we are driving a brick in to the wind constantly and you have squared it up in the wind more.
I watch my tire pressure (I keep it 38-41 psi) range, mileage and fuel use probably more than most here. I keep a log of all my fuel purchased and check it vs what vehicle mpg gauge has it at. Damn now I remember why I do.. I took my first computer class I had to "write" a computer program to do that in DOS... Damn I should have stayed with computer stuff then I said no I love to shoot guns and do stuff outside. Sorry for drifting your thread.

 

[Jaxmax]

Correct me if I’m wrong, but it isn’t the tires and wheels as you were getting the 16-20 with the large tires before the lift and Steering TSB, right? So yes mileage will drop a bit in winter, you are using remote start which with your short trips are now actually twice as long and you are not going anywhere for the first five minutes or so. Stop using remote start for a week and check back.
The 33” in your tire size should be ok on 3.73 gears, but perhaps the 12.5 could be more like 10.5-11.5 width, and light weight AT tires beat heavy mud tires everyday for MPG and day to day use, but lose in the mud big time!.....Jack

 

[GladiatorNate]

Yes, that's correct. The wheels and tires have not changed. That's why I was originally concerned with the drop in mpg. It was like something was reset.

Seems like everyone agrees that there would be a slight drop due to the leveling kit/winter gas and temps/remote starting. Perhaps that's just the nature of the beast. I just didn't expect a 2-3 mpg drop due to those factors.

 

[Scott H]

4.10 gears and you will be back to where you were at. I got 4.10 gears on my Sport Max Tow Nd I get 18.5-19 average and a little over 20 on longer trips and that's on 35's riding as seen in the picture

What lift is on this magnificent gladiator? I have a Sport S with Max tow and I'm about to put on a set of Mojave wheels with 33's/Falken wildpeak, what kind of difference can I expect? I'm hoping 1 or 2 mpg.

 

[Jeeperjamie]

What lift is on this magnificent gladiator? I have a Sport S with Max tow and I'm about to put on a set of Mojave wheels with 33's/Falken wildpeak, what kind of difference can I expect? I'm hoping 1 or 2 mpg.

That's probably about right on the Mpgs. As far as the lift, mine has a 2.5" Readylift SSt lift

kit and Rubicon Front springs. I'm running 37's now, it looks like this now.

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