haha garr nice find. srmitchell if theyre undergeared stock then they sould get theyre best highway milage stock. being that the factory might have been gearing them for highway milage then theres no way in hell people overgearing are getting better highway since over gearing will improove town milage and lessen highway milage. i dunno i just really dont believe most of the calculations people have said on this thread.
Your basic premise is incorrect that they stock gearing is for best gas mileage.
Stock is a best compromise or worst compromise depending of if you have a glass half full or half empty outlook on life.
The stock setup is a compromise between towing, town driving, and freeway driving for a wide combination of terrain. The setup for that will get you best mileage while pulling a trailer up Pikes Peak will not give you the best mileage cruising town at sea-level. The stock setup attempts to balance what the company sees as all common uses and applications of the vehicle and I am sure they need to balance a number for federal and possibly state air quality rules into stock setup.
If your particular XJ is routinely pulling trailers up Pikes Peak, being having deeper gears than your opinion might call for could actually see an improvement over stock mileage pulling a trailer up Pikes Peak.
If you drive like a blue hair and never get the throttle over half open and only coast to a stop you might get better mileage while with bigger tires and stock gears than with bigger tires and more appropriate gears. But you will also loose some acceleration and towing capacity to get that slightly better mileage.
Bottom line is that what your opinion is over geared makes a number of people including myself very happy with the performance of their Jeep.
I myself am a bit skeptical of anybody saying that they are getting 20+ with any XJ. It has the aerodynamics of a shoe box. It gets only worst with the addition of a lift, bigger tires, rock rails, skids, roof rack tire on the back stuff.
But I do think that some people can re gear and nurse a 16-18 MPG with some good tuning of the engine and armor ... Most importantly I believe they are running 55 MPH instead of 75 MPH on the freeway.
