i have an 06 Wrangler golden eagle sport. it has 4.0L 6Spd manual with 3.73 gears. came with factory 30 x 9.5s and i'm now running 31 x 10.5s. im getting about 12mpg in town and about 16.5 mpg all highway, i took a trip yesterday that was about 95% highway maybe 5% in town of which i had the cruise set on 65 the whole use of the highway. it has 77k miles and im wondering if there is anything i can do to improve the mpg. it has a k&n rechargable air filter thats all. everything else is bone stock. i run 87 regular gasoline also
03-11-2012 09:48 AM
Nothing can improve it except taking it easy. I would remove the k&n also, it only allows more dirt to get into the engine. I get 18-19 on the highway staying in the truck lanes and never going over 65.
03-11-2012 09:48 AM
16.5 is pretty good. I have the 3 speed auto with 3.55 gears and get 15.5 on the highway. Only thing to get better is park it and drive something else.
03-11-2012 09:52 AM
More tire pressure can help with MPG. Usually makes the ride too rough though.
03-11-2012 09:53 AM
On the highway I follow close to larger vehicles,let them break the wind resistance and pull you.it helps a lil
03-11-2012 10:20 AM
i definately may air up the tires a little. i drove it in the summer with the stock 30 x 9.5s on the highway and got almost a solid 19mpg. that run was all flat road and in the summer, yesterday was somewhat hills at points and the crappy winter gas we have around here. the 31s x 10.5 make a negligible difference im thinking. i would have drafted rigs yesterday but they were all going too damn slow i would have been riding their bumpers. ive had nothing but good results with k&n rechargeable filter elements in the stock airbox on any vehicle, long as they are maintained they do a fine job.
gonna replace the spark plugs and try a bottle injector cleaner in it. maybe next tank i try running premium and see if there is any improvement
just thinking about it now, i had the soft top and half doors on it also in the summer. i have the full doors and hardtop on now. i know the weight is a little different, i know the 31 x 10.5s weigh a bit more than the stock 30s, id think the lighter the jeep is the better the mpg should be on the highway.
03-11-2012 10:48 AM
The hardtop and full SHOULD give you better mileage. Reduction in wind-drag is greater than the increase in weight.
Big key to improved mileage, though, is a light foot.
03-11-2012 10:54 AM
As far as the K&N Filter goes, from what I've read, the stock air intake system can provide more air flow than the 4.0 can use at any range of operation. Aside from that, the only way an air intake could increase MPG is if it caused a leaner air/fuel mixture but that ratio is controlled by the ECU so even if you DO increase air flow, the ECU will compensate with added fuel which would give less MPG. Maybe try an OEM style replacement filter??
BTW, I'm no expert. Just a guy with the internet!! :whistling:
OOhh. The light foot thing, Try grabbing an OBDII scantool from a auto store that will display instant MPG. I drove with one for a while and noticed the best MPG when maintaining a constant speed. If you take a lot of time getting up to speed, you'll lose MPG. If you get up to speed quickly (not unnecessarily though) and maintain that speed with a light foot, it will yeild the best MPG. Any time you're accelerating, you're using a lot of fuel!
03-11-2012 11:50 AM
i used to find that i got best mpg driving without cruise. i had the oe air filter cartridge in when i got it and saw no difference, the rechargeable is just cheaper when you have multiple vehicles with them and changing is a matter of cleaning it and letting it dry and reoiling it vs going to the autoparts store to buy another. i was thinking the wider tires may create some drag. i understand getting up to speed is going to waste fuel. i dont have a professional scan tool so i cant look at mpg with it. i didnt buy the jeep for mpg, but going from seeing 18.5mpg to 16.5mpg in the course of a few months isnt encouraging. just trying to see how to get it back to that consistently for highway trips
03-11-2012 02:07 PM
Just calculated mine last week, and 16.1 MPG on 87 octane with K&N drop in. I've been running the K&N filter for 5 years and 50k now and just recently cleaned air intake and Throttle body. The K&N is doing the job just fine. I bought the K&N not for the performance, but because I have them in my other vehicles and just made $$ sense. I think the winter fuel mixture doesn't help matters. Maybe try higher octane fuel for a while and see if it improves. Good thing I didn't buy the jeep for fuel economy, LOL!
03-11-2012 02:33 PM
Did you make sure your odometer is correct after changing tire size? Verify it's giving an accurate reading. You might be getting better mileage than what's calculated. Mine's off by about 20%.
03-11-2012 03:02 PM
1 tire size with my gearing makes a small difference but i doubt 40miles to the tank difference overall, but anything is possible. my gps gives speed readout and it always seems to be dead on with the speedometer.
03-11-2012 03:27 PM
You can never improve on stock mpg of any car. You can only make it worse. The only factor affecting my mpg is how and where I drive.
03-11-2012 04:46 PM
Don't bother running premium. Your have a low compression engine that will not benefit from premium fuel.