the reason why i stay at 3500 rpms is so that i can keep up with traffic on the highway. trust me im not dumb i know that sittin at 3500 is stupid. but i have too so i can keep up.

 

You just need to get a programmer and reprogram for that tire size and your mileage should jump up to around 15 if you drive fairly OK.
Your computer is messed up trying to calculate due to less revolutions of your axles.

 

Sounds like you either have a problem as the RPM's seem high for 4th at 70, or even 3rd (should not need to go any lower than that, hills around El Paso are not that steep) or dont worry about keeping up with traffic. Set cruise at 60 and get great mpg's

 

It sounds like you are driving in rush hour traffic doing 80 mph just to survive, kind of like the Detroit area expressway traffic in Michigan. Or maybe two lane highway where there is enough traffic to be always changing speeds.

Either way, you have the wrong vehicle for it IMO. Power and weight aside, the handling and ride quality would get old. I guess I just do not see a 4" lifted Wrangler on 35's as very practical if your "always on the highway".

Initially I would think your mpg calculations are off, but if you are hitting 3500 RPM "the whole time" they are probably not. You are getting on the skinny pedal out of top gear. It has to be either accelerating, hills. high speed, or a combination of them. Or...you have a clutch/tranny slipping.

Not trying to give you a rough time. I am just thinking there is not much going to help your JK get better MPG if the above conditions exist.

Even in my Jeep, I would have to be running it pretty hard to average 9 mpg.

 

obligatory dumb question . . . you aren't in 4wd on the highway are you? I too have 4.10 auto 35" and get about 15 with a drop in k&n and superchips tuned for mpg.

something is definitely off

 

I just bought a super chip yesterday and I am getting 15.4 in town have yet to take it on the freeway~. I would definitely have someone take a look at it, 9mpg is a screw. Please keep the thread up to date, I am curious to see what the issue is. Good luck :-)

 

Did you re program after putting on the bigger tires?
I am running 37"s, with 5:13s and getting around 18 mpg...
@3500 rpm, I'm doing between 68 & 70 mph...
Not sure what you're doing wrong, but 9 mph does not compute!!

 

I don't think it's just a tire size reprogramming. Even if you assume he had the smallest stock tires (225/75r16 ~ 29.3"), the ratio for mileage adjustment is 35/29.3 = 1.19. Correcting for that only gets you up to 10.7 mpg. I don't run 35s, but that still seems low.

 

really, I don't have the technical or hardware background, but it sounds like the engine is working far to hard to move. Is that the transmission, transfer case or diff that is seizing up or something to make the engine work harder?

 

agreed, and that still wouldn't account for the ludicrously high RPM.