poor gas mileage

[greenday9d1]

I've calculated my '92 Cherokee's gas mileage to be about 12mpg, which seems very poor for a 6 cylinder engine. The engine is rebuilt by ATK and has about 1000 miles on it, the exhaust manifold is new, all the gaskets are new, the throttle position sensor is new so the tranny shifts fine. I cant find any obvious leaks. Any ideas?

[Eagle]

O2 sensor?

[martin]

Also have you put synthetic Dextron in your automatic transmisison? I did and lost 3-4 mpg in my 88 XJ. IF you have syntheric ATF in the transmission then have a flush done at a garage you trust and put in nomral Dextron, also make sure the stuff the garage uses has a certification number on the bottle.

[mudhound32]

You may also want to factor in tire size. If you went to a bigger tire without changing the gear ratio this may be causing lag. We are assuming that since this is a new engine your not hitting the accelerator hard yet? What type of driving conditions are you in?