I 4 Mpg Survey

[Oyaji]

mvusse - that's just amazing for the speeds you travel plus that your trucks are 4x4.

 

If you still have your fuel logs, consider posting over at the Fuelly site. The other I-4 Comanche there shows only 18 MPG, the I-6s range from 19.7 MPG down to a dismal 13.6, and "top of the heap and king of the mountain" is Automan's I-4 diesel, showing 29.6 MPG.

 

I am curious - how do you account for your phenomenal numbers? Driving habits? Exclusive flat-lands travel on well-maintained interstate highways? Tall skinny 6+ ply tires run at high pressure? Low-viscosity synthetic gear oil? Bed cap or tonneau cover? Other aero mods? Any tweaks you'd care to share?

[carnuck]

This past month my 4.0L auto 87 Comanche has been running about 12 mpg, but since more than 1/2 the time it's had a motor (plus my toolbox and helper) and I've been dragging other cars around at the same time. (It would be better if I had the 4.10s instead of the current 3.73s with automatic, 5 1/2" lift and 33" tires) Last night I worked on putting the rear axle in my '82 Eagle wagon and found out the XJ 8.25 I put in was longer at the pinion and the 2" (really, just return to stock height without the factory air shocks) "lift" I put in wasn't enough to use the original driveshaft anymore. The ujoint was different too.

   I couldn't tie up the shop's rack any longer, so I towed it home. Since it was raining, I'm glad I had the 440/727 in the back (they are for sale!) for ballast (plus my toolbox, towbar and helper as usual) The AW4 protested a little bit on the 20% grade hill, but only from a standstill.

[mvusse]

mvusse - that's just amazing for the speeds you travel plus that your trucks are 4x4.

 

If you still have your fuel logs, consider posting over at the Fuelly site. The other I-4 Comanche there shows only 18 MPG, the I-6s range from 19.7 MPG down to a dismal 13.6, and "top of the heap and king of the mountain" is Automan's I-4 diesel, showing 29.6 MPG.

 

I am curious - how do you account for your phenomenal numbers? Driving habits? Exclusive flat-lands travel on well-maintained interstate highways? Tall skinny 6+ ply tires run at high pressure? Low-viscosity synthetic gear oil? Bed cap or tonneau cover? Other aero mods? Any tweaks you'd care to share?

 

These number are all highway, steady speed, mostly flat. I usually run with a cap on the short bed, quite often a cap on the long bed when it still had a bed. Mixed mileage is a lot lower. For the three Jeeps I currently own, mixed mileage results:

 

1987 I4 short bed, 21 mpg and still counting

1987 I6 long bed, 17 mpg until I moved to larger tires and spent more gas off road than on.

1996 I6 Cherokee, 19 mpg until it got larger tires, people started borrowing it and I gave it to my daughter. I'm surprised it got 2 mpg better than the MJ because it has a reflashed ECM and is extremely touchy on the throttle. On the stock tires it took me a few days to learn not to smoke the tires on take off, then with 31s and 4.10 gears it was even worse.

 

For the short bed, winter highway mileage is a lot lower also due partly to winter gasoline, and in a large part due to the snow tires. This spring, after I went back to the all season tires I had to keep watching the speedometer because I kept speeding, being used to having the gas pedal at a certain height. The snow tires affect highway mileage noticeably, but doesn't seem to affect around town driving much. The cap probably helps aerodynamics on the highway, but the extra weight hurts around town.