Upstream o2

 

This. Blindly changing parts is dumb and wastes money.

 

+1 on checking for leaks, I'd bet you've a leaky injector(s), I think I read somewhere that pre-97 injectors are notoriously leaky. Fuel pressure test fo sho.

 

I hope you're not driving it until you figure out where that gas went.

 

Out the tailpipe. It was upstream o2

 

Confused. In post #10, you said you had already changed out the oxygen sensors?

 

I had an 88 xj some years ago. started getting really crappy fuel mileage. turned out to be leaky fuel injectors. The fuel ran down onto the hot exhaust manifold and vaporized so no drips below the jeep. If you really are getting anywhere near that crappy of fuel mileage then you should be able to smell unburned fuel in the exhaust. If not then the fuel is going elsewhere besides out through the exhaust. Pouring that much fuel though a 4.0 if it is even possible for it to run with that much fuel going through it will leave plenty unburned.

 

Don't mean the one they gave me was good