so the jeep went on the road for the first couple of days i figured i would put about 30 or 40 miles on it and fill it up again so i did that today and figured out that i get 12 miles to the gallon wiht my 93 jeep grand cherokee AWD. I put a rusty's air tube on it, definitly got some performance from it. but still that 12 miles to the gallon. anyone have any ideas. am really thinking about the fitch system.

Not enough miles to get a reliable milage estimate..
Take it to your favorite station and fill it all the way up. Then run it for days or weeks if it takes it until it is near empty. Then take it back to the SAME PUMP and fill it again.. now you will have a better idea of what your milage will be.
Please believe me when I say: ONLY your driving habits will increase your milage... NOTHING you can purchase and install will get you better milage.
AND that tube you have installed..It may make more noise but it didn't help your milage.
Big JIm <img src="/forums/images/graemlins/pfft.gif" alt="" />

One contributor to poor mileage is the AWD system. That means that both axles are engaged all of the time, which costs additional fuel. That's why lock-out hubs were made for part-time 4WD systems - to get the front wheels free-wheeling.

I don't know if you have a V8 in your Grand, but that will be another contributor to fuel costs. Admittedly, they're more fun, and I have v8 engines in both of my 4x4s.

Take BigJim's advice. I'd do it twice - once with mostly driving around town, and again sometime on a trip where most or all of the driving is freeway.

But, in the end, keep in mind that Jeeps were designed for fun and utility - not for good fuel mileage.