You are not going to lose enough weight to warrant it and still retain creature comforts. These rigs roll off the line at 3000-3500 lbs and its already a brick on wheels. Easiest way to pick up mileage on an XJ is proper tune-up, stock highway or road tires, synthetic fluids, non ethanol gas, reduced idling and driving like a grandma. Perhaps try researching alternate travel routes to reduce stop lights, rapid acceleration and deceleration and maintain a more consistant speed. i experimented with my route when i had a 20 mile commute, and by changing routes to a travel with less stops and more consistent speeds, i was able to gain 3 mpg over driving through town and it only added 3 minutes of travel time.

 

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