Been a Jeep owner for a few years now and just made the jump into a jk. Mine will arrive on Monday. I've read a hundred threads on increasing mpg already and figured I'd ask for any specific pointers. I know what I'm getting into, but every little bit helps. Will a performance muffler make a difference by itself or do I need to gut the whole exhaust system to see any real difference? Baby steps.

 

About the only way I have seen to improve mpg is to install a full superchager. Remove weight, run smaller tires and keep the rpm down under 2000 will do more for you then throwing money at it changing air filters and exhaust.

 

Closely related: Keep speed at 65 MPH or lower; avoid anything faster. Will give you way more increased mileage than anything easily accomplished (IOW: A total redesign). Expect 2-3 MPG improvement over driving the posted speed limits on highways and Interstates (at least in those states with reasonable speed limits).

A further thought experiment: All manufacturers that sell cars/light trucks in the U.S. are under considerable pressure every year to meet the CAFE standards. If there were easy mileage to get by changing the programming, air filter or exhaust, don't you think they'd do that? The reason the Wrangler is not offered with a Hemi is because Jeep uses the higher mileage of the smaller engine to meet those CAFE standards by forcing their fanatical fans to buy the lesser powered engine. If you were Jeep/Chrysler/Fiat and had a free hand, wouldn't you rather offer the much higher profit margin Hemi to those fans who are begging for it? Anyone looking for better gas mileage is buying the wrong vehicle.

 

Baby steps...turn off the A/C when wheeling. Don't spill your extra gas supply on the trail. Leave the portable shower at home to save weight, and don't let the dog stick his head above the windshield too much, it creates drag.

The wizards have already spoken truth about forced air, smaller tires, and driving slow enough to aggravate your grandmother, so I leave you with practical ways to increase fuel economy for Jeep's intended purpose.

 

First time I've ever thought about dog induced wind drag. That's pretty funny Damnit Fido put your head in the Jeep your killing my MPG!

 

Had anybody experimented with not filling up the tank all the way? Seems like 20 gallons is a load to lug around for no reason. I'm not trying to get 30 mpg here. But surely don't want to be under 10 either. Thanks for the tips.

 

I get 15 mpg with 40's on a 5000+ pound JK 6 speed 5.13 gears. My wife gets 22 mpg on her 2007 JKU 6 speed with 32's and 4.10 gears. I doubt you will see 10 mpg unless you drive like a dumbass.

 

I wouldn't recommend it, seeing how the JK's range is pretty limited anyway. I'd rather keep a full tank even with the extra weight.

Regular gasoline weighs approx 6.1lbs per gallon. With 18.5 gallons in the tank, you're only carrying ~ 113 lbs in gas, and that's only temporarily as the engine sucks it down.

My basis for understanding is having added larger, heavier tires, and a couple hundred pounds of additional weight with increased aerodynamic drag (lift, tires, steel bumpers and carrier), and my average MPG only dropped about 2-ish mpg.

 

That's good to know. I'll hover somewhere between stock and dumbass!

 

Gas evaporates. I've read the more gas you have in your tank the less evaporation you will have. So there's no winning.