WJ Jeep Grand Cherokee sucess, is relative aparantly

[Tezzating]

Hey guys, I just wanted to gripe with some folks who'd understand.. For 2 years now my wifes complained about her Pontiac Sunfire and how she wants a Jeep SUV. So I traded off her Sunfire for a 2000 Grand Cherokee Laredo, 6 cylinder + 4 speed auto & 4x4.

Serviced the diff's with synthetic 80W90, trans with synth ATF+4, engine with synth Rotella oil, new spark plugs, intake cleaned out, fresh air filter, removed roof rack and 35PSI in the tires.

EPA is 14 City, 19 Highway. ACTUAL is 16.2 City, 22.8 Highway.

To me thats awesome gains considering there's no aero, no retuning or anything else just maintenance. To her its "terrible".

Its never occured to her going to an engine with 2 more cylinders, double the capacity, a 4 speed auto instead of 5 speed manual, extra transmission (tranfser case), two more driven wheels and extra 1500lbs of vehicle might have a negative effect on fuel economy.

The good news is, she's a bit more interested in driving efficiently now. So on the road trip yesterday we discussed and practiced drafting techniques and picking smoothest lines and such.

[comptiger5000]

I've gotten 23-24 mpg at 60mph out of my mom's almost identical 4.0 WJ (hers has Quadra-drive and 3.73 gears). My friend has one also (standard 3.55 gearing) and has pulled just about 25 out of it (before he lifted it).

Your city mileage is actually pretty good. In what I'd consider city, I've never seen more than 14 or so out of one of those. For what the vehicle is, and how capable they are off-road, etc, the mpg isn't too bad. Of course, compared to an econobox, it still sucks.

Drafting helps greatly on the highway with these, being that the aerodynamics are pretty bad. According to the instant mpg display on my mom's, drafting a semi about 70-80 feet back at 65mph is worth 4 - 5 mpg gain. Unfortunately, my V8 one only sees 2 mpg or so from this, as it's got a lot more engine, and the gearing isn't any taller, so it's already below the efficient part of its load curve.

[Tezzating]

Thanks for the feedback ! Its good to know our results are comparable to others. TBH I'm sure once we have 2 foot of snow (Hello from Canada !) she'll forget all about the extra $40 a month in gas..

I think highway speeds there's a speed at which we'd enjoy greatest efficiency. The above result was gained at an average of 75mph, doing 65mph would be better I think.

I've been looking at the front end and will make some changes which will help with highway:
- Someones chopped the inner guards, probably to fit a larger tire, but thats gotta be bad for aero.
- The grills for fog lamps are open, so I'll fill those when I fix the inner guards
- I saw a thread with a guy running an XJ on here, he gained MPG by blocking 5 of the 7 grill vents (Canadian winter coming, so this isnt a bad idea either way !)

I'm swapping in an electric fan on my truck and if that works out good, I'm going to swap the Jeeps too.

[comptiger5000]

The inner wheel-well guards may or may not make much difference, as they're not particularly exposed. Blocking the fog light holes would be worth it though.

That Jeep should already have an electric fan. If it has a mech fan, then it has both (tow package), and you're fine to pull the mech fan and run just the electric.

Also, be careful with grill blocking in warm weather, as the grille was made huge on these things for a reason.

[Tezzating]

Originally Posted by comptiger5000

The inner wheel-well guards may or may not make much difference, as they're not particularly exposed. Blocking the fog light holes would be worth it though.

That Jeep should already have an electric fan. If it has a mech fan, then it has both (tow package), and you're fine to pull the mech fan and run just the electric.

Also, be careful with grill blocking in warm weather, as the grille was made huge on these things for a reason.

Yes its got a tow package fitted, and has the electric fan. I've already deleted the wiring for the trailer, and have ben considering removing the tow hitch. So only the tow package models had the crank fan ? Thats good news ! I'll remove the tow hitch, crank fan and change the thermo-stat & coolant this weekend in that case