Not bad for a gasser on 37s

[RJinPV]

Ok. I was joking (a little) but you can see everyone is skeptical there isn't an error lurking in here somewhere. Did you update the computer settings to indicate the proper tire size? Does the computer think you have 40" tires by mistake? The only other explanation is you lightweighted your rig by tossing the spare tire, the back seat, any skid plates, hoods, fenders, etc to offset the 100 lbs of additional tire weight the 37's give you plus their increased rolling resistance. Physics is physics.

Sponsored

 

[ScottBeach]

Its the helium in the tires.

 

[ScottBeach]

Or is that run down hill both ways? I am stock tires on flat florida ground if i reset at speed on the hwy already at 70 cruise set and never go over a bridge i might see 22.5.
With getting to the hwy and having to hump over bridges real world is about 20.3

 

[Kajo]

It seems feasible to me. In comparison, my family trip this summer through Virginia, Tennessee, and North Carolina in my 2020 Rubicon 3.6L with 37" KO2(c)s on stock rims and 4.10 gears I averaged 21.4 on the highway. This was over the span of 2626 miles with 4 adults plus luggage, cooler, and recovery gear in the covered bed. Speedo is dead on with my GPS (Tire size adjusted by Tazer) and cruising 2-3 mph over the speed limit most of the time.

Now I did spend 2 days wheeling in Windrock, 3 days in the Great Smokey Mountains National Park and 1 day wheeling at Uwharrie. On those days my mileage was a lot less which is to be expected.

 

[ThatStinging_Jeep]

I know that's a damn lie ,I was getting 16-18 mpgs on my stock jt gasser,only had a bumper,sliders and skidplates and some heavy ass black rhino wheels lol

Unless there's a mighty Backwind or a angel pushing your jeep yeah I'll believe you,

I never trust that Guage to begin with just paper and a pencil or a calculator of course

 

[Panda]

Ok. I was joking (a little) but you can see everyone is skeptical there isn't an error lurking in here somewhere. Did you update the computer settings to indicate the proper tire size? Does the computer think you have 40" tires by mistake? The only other explanation is you lightweighted your rig by tossing the spare tire, the back seat, any skid plates, hoods, fenders, etc to offset the 100 lbs of additional tire weight the 37's give you plus their increased rolling resistance. Physics is physics.

I did update the computer, and you’re correct on the light weight setup. No backseat or spare. I still have the stock bumper and fenders. I’ve always had decent gas mileage for it being a brick on wheels. I get around 17 mpg in the city and am usually around 19 to 20 highway. This definitely drops down a little bit in cold weather though.

 

[AmishMike]

You said '37 Gasser right?

 

[JTR178]

OP sits on a throne of lies.

 

[BAT]

Just another reason I do not believe anyone's gas mileage tales. I am sitting almost stock. I have Rubi Take offs and an Arcus Front Bumper with winch/synthetic rope. No lift, no bigger tires, no change in geometry of the truck to get the perfect angle for glamor shots. Its a DD for the most part on my 100 miles round trip commutes. I don't ever even sniff that kind of mileage no matter how I drive whether it be 50 MPH or 80 MPG. I just recently did a trip of around 450 miles each way pure flatter than flat and almost all highway with not a lot of traffic so it was usually steady at 65 -70 mostly. No load in the bed with just myself passenger who might have weight a buck fifty. I didn't come close to sniffing 20+ MPG. The only time I ever got into the 20's was bone stock on the freeway.
My only conclusion is again that I did not get one of those special engines that seem to be out there but I sure would like one (LOL)

 

[RJinPV]

I did update the computer, and you’re correct on the light weight setup. No backseat or spare. I still have the stock bumper and fenders. I’ve always had decent gas mileage for it being a brick on wheels. I get around 17 mpg in the city and am usually around 19 to 20 highway. This definitely drops down a little bit in cold weather though.

Okay. Any other tricks/techniques you can share with the rest of US? Maybe we can all save a little $$. What brand and model of tires are you running? I bet you inflate on the high side too. I always run 1-2 PSI higher than the door sticker recommendation

Do you ever double check the computer MPG calculation? I have recorded that on my rigs for years. So, I decided to check the last 6 tanks of fuel. Mine reads an average of 1.0% high (computer overestimates) over those 6 tankfuls. This is actually a lot better than I thought it was going to be. However the variation is quite high. One of those tanks it read 6.6% high. So maybe on the run you're showing us, the computer was off by 1-2 mpg?

 

[bleda2002]

Not that i'm anywhere near the op's numbers, but I have found I can gain 2 mpg city on 39's if i use the cruise control to get going from a stop instead of my foot. That brings me up to around 15.5 from 13.5

 

[Panda]

Okay. Any other tricks/techniques you can share with the rest of US? Maybe we can all save a little $$. What brand and model of tires are you running? I bet you inflate on the high side too. I always run 1-2 PSI higher than the door sticker recommendation

Do you ever double check the computer MPG calculation? I have recorded that on my rigs for years. So, I decided to check the last 6 tanks of fuel. Mine reads an average of 1.0% high (computer overestimates) over those 6 tankfuls. This is actually a lot better than I thought it was going to be. However the variation is quite high. One of those tanks it read 6.6% high. So maybe on the run you're showing us, the computer was off by 1-2 mpg?

I’ve never double checked the computer mpg calculation. I have cooper stt pros on fuel zephyr wheels. I keep my psi around 33 on street and depending on the trail I will air down between 12-20 psi. I’m not sure it’s really a trick, but when I drive I try to avoid using the brake for stop and go situations. Instead I will just coast a little more and give the driver in front of me more space. I honestly couldn’t tell you if it helps that much with mpg or not. I do it so I don’t get rear ended while in traffic (which has happened in other vehicles). I do the same thing with red lights, there is no reason for me to rush to a red light to hurry up and stop, and is usually faster to time the green light anyway.

 

[RJinPV]

I’ve never double checked the computer mpg calculation. I have cooper stt pros on fuel zephyr wheels. I keep my psi around 33 on street and depending on the trail I will air down between 12-20 psi. I’m not sure it’s really a trick, but when I drive I try to avoid using the brake for stop and go situations. Instead I will just coast a little more and give the driver in front of me more space. I honestly couldn’t tell you if it helps that much with mpg or not. I do it so I don’t get rear ended while in traffic (which has happened in other vehicles). I do the same thing with red lights, there is no reason for me to rush to a red light to hurry up and stop, and is usually faster to time the green light anyway.

I use those same driving techniques too. Kinetic energy is turned into waste heat when you use your brakes so why use them when you don't need to?

 

[AmishMike]

'20 JTR automatic, stock suspension Geolander A/T's 315/70R17 so 34"+, no recalibration, Warn winch, plastic bumper, aluminum full height rack 20-21 mpg average.
60 miles commute, 38 is highway 22 back roads. I find that I can consistently beat cruise control. They key is to anticipate the road, not just for slow downs but for pitch and hills. That and keep it under 75 mph.

 

[Dunks001]

Sport with max tow 4.10 gearing

I also have a max tow on 37’s. The computer exaggerates 9 out of 10 times. Did you verify after filling up? Mine is not photoshopped. Yours looks suspicious. ). Mine was doing 55mph on Natchez Trace Parkway. Verified by filling up and doing a calculation
Like others have said, tail wind, downhill and drafting behind a semi are the only way to get over 20mpg on a highway. Getting 8th gear over 70mph is hard. Congratulations for making an interesting post.

Sponsored