Does anyone have tips for increasing gas mileage?

[Jackjack97]

does anyone have tips for increasing gas mileage? I know damn well tjs have horrible gas mileage and I don’t expect a whole lot but I’m pretty low at about 11.5-12 mpg. If this is normal for a tj lmk. Currently I am on 31s at stock height and the gearing is super bad. The previous owner just slapped on some 12.5 31 r15 on and expected it to be good with 3.07 gears. Could the gearing be my problem?

 

[KingCarGuyZ]

does anyone have tips for increasing gas mileage? I know damn well tjs have horrible gas mileage and I don’t expect a whole lot but I’m pretty low at about 11.5-12 mpg. If this is normal for a tj lmk. Currently I am on 31s at stock height and the gearing is super bad. The previous owner just slapped on some 12.5 31 r15 on and expected it to be good with 3.07 gears. Could the gearing be my problem?

A/T or M/T? 4.0 or 4cyl?

I'm 4.0 5spd (NV3550) on 31's i get 12-13 city, and I got 15 HWY last Week! 11-12 seems low. but not by to much.

 

[Jackjack97]

A/T or M/T? 4.0 or 4cyl?

I'm 4.0 5spd (NV3550) on 31's i get 12-13 city, and I got 15 HWY last Week! 11-12 seems low. but not by to much.

I’ve got a 97 with 4.0 and 5spd tires are all terrains. I have seen people who are saying their mileage is about like yours or a little higher and that is where my concerns are coming from

 

[RMETeeJay]

You're just a little lower than expected, I think. In order to maybe do better, take a look at the following physical parameters:

1. When was your last full tuneup (plugs, wires, cap & rotor, air filter)?
2. What temperature is your CTS reporting (via OBDII) after engine is fully warmed up?
3. What PSI are you running on the tires?

If all of those items check out, a lot of it is behavioral (how you drive), which is hard to quantify. For me, if I'm trying to save gas, I stay back from the car ahead and shift intelligently to avoid repeated braking/acceleration. At highway speeds, once you go over approximately 60 your MPG will drop.

 

[Chris]

Replace your O2 sensors:

The Official Jeep Wrangler TJ Oxygen (O2) Sensor Thread

 

[1515art]

does anyone have tips for increasing gas mileage? I know damn well tjs have horrible gas mileage and I don’t expect a whole lot but I’m pretty low at about 11.5-12 mpg. If this is normal for a tj lmk. Currently I am on 31s at stock height and the gearing is super bad. The previous owner just slapped on some 12.5 31 r15 on and expected it to be good with 3.07 gears. Could the gearing be my problem?

take it to auto zone if you don’t have access to a scanner they will check it for free (?), and find out the LTFT long term fuel trIm low numbers and you can rule out engine problems, high values you may be able to improve fuel economy from an existing vacuum leak, sensor issue?

 

[Lou]

Ever since I put 35s on I’ve never got better than 10-13 mpg.

 

[1515art]

The LTFT is a learn baseline from the computer and establishes a new zero starting point for the STFT set by the computer trying to maintain a 14.7 to 1 fuel ratio in relation to intake air in combination with the other sensors.

 

[Frankm]

Assuming your vehicle in tune, etc biggest MPG improvement comes from your right foot.... light on throttle and keep rpms low and steady. At least on my 4.0 that works for me. I get 17 mpg in town and 18-19 mpg on road. I only drive 60 ish and I ll NEVER win the stoplight grandprix but usually end up 1-2 vehicles behind the knot heads at the next light !!

 

[Mr. Bills]

Assuming your vehicle in tune, etc., biggest MPG improvement comes from your right foot.... light on throttle and keep rpms low and steady.

^^ This.

Or only drive downhill.

 

[Frankm]

Mr Bills 100% correct, down hill is Best!

 

[Artsifrtsi]

I get 15-16mpg (220-250 miles per tank) with 4.0l, 6sp, 3.07, and 31's. Oddly, I get better mileage in it than my wife does, and I shift about 3-4k RPM, and she shifts 1.5-2k RPM.

 

[WWII Jeeper]

I recently returned from a trip to California and back via I-80. My 06 X, 4.0, 6 spd man, is stock suspension, 1 inch body lift, stock air cleaner, and throttle body, with 31's on 16 inch wheels, and 118K miles. if I remember, same gearing as yours.

my high was 19 mpg, running at 60-65 mph, and dropped to 17 mpg running 75-80 across Nevada. I run this route frequently, and I'm constantly checking my mileage.

The only thing different on this trip was the fact that I totally forgot to change my air filter (I always change it before a California trip), so who knows, I may have been able to break 20 mpg. I've done it a bunch of times in past trips.

Around town I typically get 15 mpg.

I've tried the cold air intakes, the throttle body spacers, different gas additive goo, different spark plugs, and none of it enhanced the performance and gas mileage. Actually, my mileage decreased.

Sorry to make a short story long. The point is: Don't waste money on All of the "enhancers" or performance mods claiming to increase gas mileage.

Take that money and make sure your maintenance is up to date, and your sensors are good quality. Just because the Jeep doesn't throw a code, doesn't mean the sensor is good.

I do pay attention to my shifting points and rpm's as well.

Ray

 

[Jackjack97]

You're just a little lower than expected, I think. In order to maybe do better, take a look at the following physical parameters:

1. When was your last full tuneup (plugs, wires, cap & rotor, air filter)?
2. What temperature is your CTS reporting (via OBDII) after engine is fully warmed up?
3. What PSI are you running on the tires?

If all of those items check out, a lot of it is behavioral (how you drive), which is hard to quantify. For me, if I'm trying to save gas, I stay back from the car ahead and shift intelligently to avoid repeated braking/acceleration. At highway speeds, once you go over approximately 60 your MPG will drop.

Full tune up was done about a year ago along with some other things like seafoam and injector cleaner to try to get misfire to go away

 

[Jackjack97]

I get 15-16mpg (220-250 miles per tank) with 4.0l, 6sp, 3.07, and 31's. Oddly, I get better mileage in it than my wife does, and I shift about 3-4k RPM, and she shifts 1.5-2k RPM.

I also shift around 3-4

 

[DK-RESTO]

4.0 5spd here w/ 4" lift and 33"s and I get 16 consistently. new O2 sensors and tuneup always recommended

 

[Viking Jeeper]

On 35's I've hit 14 twice, both times crusing at 50-60 mph. I usually get 12-13. My speedometer/odometer is correct.

 

[1515art]

I've tried the cold air intakes, the throttle body spacers, different gas additive goo, different spark plugs, and none of it enhanced the performance and gas mileage. Actually, my mileage decreased.

the problem if I understand all this, electronically controlled fuel injection is already running as efficiently as possible within the limits established by emission settings, with everything operating at peak performance.

the computer will fight any effort interferring with the prime objective of maintaining a set air to fuel ratio. better performance I think can only be achieved in very small increments small enough to be ignored within the tolerances set by the programming.

because the adjustments by the computer can have fairly wide limits before indicating a problem (mil) it may be adjusting against the modification by sending more fuel in a longer injector pulse to compensate decreasing fuel economy.

 

[Jerry Bransford]

Your engine is slightly lugging/operating very inefficiently at rpms that are lower than optimal for even 31's. Raising your rpms by regearing your axles should increase your mpg. Mine went from sub-12 to around 14.6 after regearing my axles to raise my rpms up to where the engine operates more efficiently. Lower rpms like your 3.07 axle ratio is causing does not usually mean better mpg.

Also, make sure your tires are properly inflated, I'd be at no less than 31 psi for your 31's.

The last mechanical problem that will cause reduced mpg is a bad upstream O2 sensor. They go bad just like spark plugs do and a bad upstream O2 sensor could be erroneously telling the computer your fuel mixture is too lean which would cause the computer to set it richer. Since a defective upstream O2 sensor would never tell the computer the mixture is correct the computer would keep raising the amount of fuel sprayed until the mixture is full-rich which will destroy the MPG. But your present sub-12 isn't so bad that I'd suspect that.

The 3 things I'd try are 1) Slow down. 2) Make sure your tires are properly inflated. And if $$$ is not a huge issue I'd regear your axles to a more appropriate ratio like 4.10. Not only should it help your mpg, it would provide a dramatic (!!!) performance boost. Your TJ is a dog, performance-wise, with 31" tires and 3.07 gearing.

 

[eastbloc]

O2 sensors typically drop you below 13mpg, rest is you.
13- 15mph or 220-250mile range is the norm.
unmolested can see between 15 - 17 on a good day.

Once in blue moon, uni-Jeep shows up here and claims 17 - 21mpg from running on unicorn farts. Stay away from them, they are weird.