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DD Fuel Efficiency / Performance Upgrades?

S

SharkXJ

NAXJA Member #1177
Location
San Jose, CA
Hey ya'all....

My daily 80 mile round trip, 400 mile per week communte to work everyday is workin' my heep. I'm getting about 17 mpg which isn't bad considering 35's and all of the weight.

I want to get another XJ and keep it stock BUT I was wondering what I could do to get around 20 to 22 mpg out of one? I know, I know - I should get a Japanese car but I know XJ's and I am more comfortable buying one with higher mileage than I am a foreign car.

Here's what i'm thinking - Switch to a 15x8 rim and run a slightly lower profile, light truck tire. Then throw on a cold air intake, and a cat back sysem of some sort. then of course do a total fuel system clean. With that I am thinking I could get about 8 to 13 more HP which in turn could get the mpg up a little.

How about plugs and a coil pack? Is there an after market coil pack or Distributor Cap System to increase effeciency?

Thanks a bunch!!!

~Mark
 
I got that with my stock 2000 (AW4) rolling on 235/70/16's (itty bitty tires).
Only thing that wasn't stock was the head, which was a '93 and then a '93 style manifold keeping the 2" outlet to just under the bell, then up to 2/14 from bell to cat and 2 1/2 from there back and back to 2 1/4" past the muffler ... sound wierd but it worked.

On oil changes I used 1 bottle of Syn to three bottles of Dino and it kept the motor clean, and the air filter was changed evey 10-12 months.
I got around 23mpg all highway as I had to drive 5ookm to get to work and another 500 on the way back a week later.

Haven't calculated recently but I'm about 17mpg now with 255/70/18 '08 Sahara stockers, and 4.56 gears on a ~5.5" lift.
 
My DD gets 30 mpg......:D I've gotten around 21 mpg on 32's and stock gears but don't see myself getting any better than that after regear. Maybe after I do some motor work but to me, its a Jeep. The bad mileage comes with the territory.
 
I can only speak from my experience with my 99 xj but I got 18 mpg around town and 25 mpg on a trip running 215 75 15, 4.0 ax15 w/355 gear. Now I have 31's same gear and a 4.5 RE superflex which took me to 14.5 mpg city and 20I Hwy.
hope this helps.
HU
 
The best upgrade you can make to fuel economy is the driver. Get an OBDII scanner with real time instant/average fuel economy and an analog vacuum gauge. Even if it isn't 100% accurate on what your actual MPG is it is a useful tool in figuring out what helps and hurts fuel economy. Find your ideal cruising speed on the highway. Keeping engine vacuum as low as possible will get you generally better mpg. Once you have decent baselines is when you can make modifications. You will know what works and what does not.

There is so much BS about fuel economy on Jeep forums because jeeps get bad mileage and are not fast or even large/useful for truck stuff. Most are never satisfied with their jeeps fuel mileage. When you have something fast with lots of power that gets poor mileage you don't care nearly as much because you can always say to yourself "atleast it's fast" or "atleast this 3/4 ton truck can tow a 14,000lbs"

See a stoplight turning yellow way ahead? Coast to it and sometimes braking slightly so you are still rolling when you get to it and it turns green you don't have to use as much energy to get moving again. Yes, 10+ people will look at you like you have 2 heads as they haul ass past you just to jam on the brakes and sit idling at the red light as you coast to it. If there is a lane open you will actually shoot past them because you are still moving when they are accelerating from ZERO MPH. Yes some people find this annoying. Do you really care what they think? They are burning more fuel than your lifted xj on 35's than their V6 Honda Accord during this situation. Screw em. This only works on timmed red lights and not the ones that do not change unless you trip the magnetic/weight sensor.
 
How you drive has a lot to do with MPG
Click to expand...

Yep, I can add another 3mpg if I wasn't pushing the clock (and the pedal) all the time. Eventually I'll just leave early and slow down some ... but winter hasn't hit yet.
 
65mph requires 12% more fuel than 55mph
75mph requires 25% more fuel than 55mph

Slow down and save fuel. Use synthetic oil, injector cleaner every few tankfulls.
 
I have a stone stock XJ for my 80 mile commute and can hit 24mpg if I accelerate like granny, never break 65 mph, and throw it in neutral on the big downhills. I keep the stock sized tires and bump up the pressure a little. A good tune up is fine, the stock equipment is all intact.
 
what i recommend is you go to ultra-guage.com
there you can buy an obd2 scanner that doubles as on on dash display of every sensor that you have in your car, personally i use the TPS sensor to know where my foot is at on the accelerator, and it also gives me instantaneous MPG plus average so im always concious of how im driving.
 
Narrow tires on lightweight aluminum wheels, and over inflate them.

Remove all interior panels, carpet, passenger seats, spare tire and jack, radio and speakers.

x2 on getting a 2wd. But get a 2wd with a 5 speed.

Lower it an inch or so and remove the factory roof rack and passenger side mirror. Remove any skid plating. Buy a smaller battery. Remove the a/c. Run a flush hubcap on all corners. Skirt the rear wheel wells.

Maintain 55mph and try drafting semi trucks.
 
Talyn said:
You don't know where your foot is otherwise?
Click to expand...

That made my day ... it's been a slow day so far ... but still funny as hell.

goblazers_6 said:
Narrow tires on lightweight aluminum wheels, and over inflate them.

Remove all interior panels, carpet, passenger seats, spare tire and jack, radio and speakers.

x2 on getting a 2wd. But get a 2wd with a 5 speed.

Lower it an inch or so and remove the factory roof rack and passenger side mirror. Remove any skid plating. Buy a smaller battery. Remove the a/c. Run a flush hubcap on all corners. Skirt the rear wheel wells.
Click to expand...

For all that work just go buy a compact in decent shape and enjoy 30+ mpg (plus, some poor unsuspecting Cherokee will thank you for it). It just sounds painful for the poor XJ.
Of note also is higher inflation pressures may lead to handling issues as well, try driving anything at 43psi and you'll get an idea what I mean (can you say squirrely) ... the PO of my wife's JK did that, why? I don't know, sure didn't help mileage that's for sure. If I get above 30psi in my XJ she starts to get twitchy as well.


Maintain 55mph and try drafting semi trucks.
Click to expand...

they really love it when we do that ... hehe


In all honesty, if you wanted good gas mileage ... a jeep (YJ/TJ/XJ/ZJ/JK ...) isn't the best choice ... or even a good choice. They are what they are and that's why we buy them.
 
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