What are the secret MPG mods???

Ok,
my reason for starting this thread goes like like this.
After doing searches and reading posts on MPG I've come across three different camps which XJer's belong to.

1) My MPG just plain sucks...
2) I get the the average 20 MPG on highway and 15-16 in the city.
3) My MPG has just plain gone through the roof, 20+ MPG!!!

I can understand how camp 1) & 2) get their MPG, but camp 3) makes their claims but never divulge their secrets.

At this point I am now calling everyone from camp 3) to come forward and confess how they acheived their success.

What modifications to the 4.0 did you all make to create such efficient machines? Your words will be invaluable to the rest of us...Also please list what your average MPG city/hwy is.

Weird thing is that when I drive to NYC from Knoxville, my MPG shoots up 2.5-3mpg on the highway as soon as I fill up past the West Virginia border :dunno:

Drewman said:

What are the secret MPG mods???

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Keep it stock

Kejtar said:

Keep it stock

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Actually I should probably be more serious , but you have asked a very loaded question. When people post their MPG results, you have to keep in mind their location. Depending on where they are, there are different additives with different seasons. Also different altitudes have different effect on the MPG. Also there is an issue of driving habits and the maintenance of their XJ's. And lets not forget those that have speedo gears which are wrong for their vehicles and thus whatever they post is already tainted by the fact that their speedo is off.....

Kejtar

I retained my stock gas mileage, 19 mpg highway, 15 city. Synthetics everywhere and I try to keep the gas pedal off the floor.

--Matt

I got a new K&N airfilter (stock one was brown with rocks in it) and i get 45% better mileage

Well, I pick up about 2mpg crossing into AZ or NV - but that's no mystery. CA requires the use of MTBE as a fuel pollutant, while AZ and NV do not. Therefore, I get better fuel mileage since I start using cleaner fuel.

Check with Dino Savva's homepage (we know him here as Dr. Dyno) for some good homebrew ideas for increasing both power and efficiency measurably. These goals are not mutually exclusive - increasing efficiency with which fuel is burned will increase available power. Most mods that increase power in a modest fashion will also serve to reduce tailpipe emissions, as will using cleaner fuel. Just a few thought... I haven't had half a chance to work out some mods specific to the 4.0 myself, so start with Dino's page for some ideas...

5-90

Basically what 5-90 said. I'm averaging 20.7mpg in mixed city/highway driving so it's at the same level as when my engine was stock. The only difference is that I've gained about 25% more HP and 17% more torque than stock with my mods and I'm still using the same amount of fuel (despite spending more time sitting in slow traffic), so the engine's definitely much more efficient.
Getting good gas mileage isn't rocket science. All you need is:

1. A light right foot
2. Stock or near stock size tires to minimize rolling resistance and reduce inertial drag on the drivetrain
3. Remove unnecessary weight and especially those items that ruin aerodynamics (like roof racks, winches, bullbars)
4. Avoid suspension lifts. A lift ruins aerodynamic efficiency and increases gas consumption.
5. Use the highest gear possible without lugging the engine
6. Maintain the engine and the rest of the vehicle in top condition, with the engine in a proper state of tune
7. Make sure tires are properly inflated
8. Drive smoothly. Sudden sharp acceleration and braking manoeuvres increase gas consumption
9. Stay below 3000rpm as much as possible
10. Stay in 2WD if you have the NP242 and only use 4WD full-time if the road is slippery

I fall into group 2 - 15 - 16 around town and 20 on a long Freeway trip. about 1 MPG less with the stroker than with the 4.0. And we have MBTE in Winter here in the Northeast, so mileage does decrease. Eagle is the only one who has documented 25+ MPG (with his 88 5 spd) and I've ridden with him and he uses very little throttle!!

I've been in the 22-24 mpg neighborhood. Biggest thing is to lose some weight in your right foot. Only mod on my 4.0 is a K&N on a Rusty's air tube.

Thanks for those answers guys.

I have K&N on the way, can't wait fot that 45% increase in fuel economy. :roflmao:

I think that should be 4.5%

Gojeep said:

I think that should be 4.5%

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Agreed. I didn't notice any increased MPG with my K&N cone. I have since went back to air box/flat filter, due to way too much mud and junk getting on that filter. Plus it left a residue in the air tube. I don't think that filter stops as much as it says it does.

I got 5-7% better fitting a 2000 intake and another 5% after the electric fan conversion. Re-gearing back to stock made running around town and off road better but lost some hwy mileage. On average it was the same after a big 12,000 kms trip. But at least I got the power back for no mileage expense

i get about 17 average with mostly around town.. my right foot is my biggest problem.. as a side-note... i left for Moab in october with about 150 miles on a new engine.. average MPG for the first 1000 miles was 11 MPG!!! 2nd 1000 was 13.. after 10 days and 5000 miles of 80 - 90 MPH breakin period i was at 19 MPG by the time i got home...... (damn! that was alot of $$$)
mike