yeah, i'm not sure how chuck got his mpg calculated, it's not gallons/mile

guidelines for calculating correct mpg

- to calculate mpg accurately top-up the tank, reset the trip or write down the odometer reading and drive a bunch, then top-up again and calculate the number of miles driven

- pay attention on how the Jeep is positioned at the gas pump, the YJ/TJ gas tank is notorious for having differences while not level, best to average the mpg over several tanks to avoid errors.

- use the numbers behind the decimal point (10.999 gallons is just that and not 10 gallons)

- calculate mpg like this mpg=<miles_driven>/<gallons_including_decimal_places>

common errors when calculating mpg that result in ridiculous numbers:

- if your tank shows 3/4 full it doesn't mean you only used 5 gallons (or whatever a 1/4 means in your case)

- do not count the miles while it's been towed

- if only driven on the highway with favorable wind the Jeep acts like a big sail, if you want to make it accurate drive the same distance back and re-calculate, better to average mpg over several tanks

- doesn't count if driven down the mountain, you need to calculate both ways, same thing here - average works better

- i'm sure there's other factors that I can't think of, feel free to contribute

- EDIT: i remembered another one - larger tires without speedo recalibration can result in lower calculated mpg than actual, going the other way are smaller diameter tires or "longer" Ring & Pinion kits (odo/speedo showing more than actual speed/miles driven)

- EDIT2: another one - doesn't count either if you draft a trailer, big truck or farm vehicles, it's your skill and patience and not real mpg.

if you're sure the Jeep is really good on gas then take the motor out and install it in a Smart car or a Fiat 500, it will get better mpg than the original and be as fast as a Corvette

if in doubt you can always check the published numbers, if you're off by too much might want to review the calculations

http://www.fueleconomy.gov/feg/noframes/19193.shtml