P0442, evap system fault(leak detected IIRC). How long since your last oil change, what brand and weight of oil do you use, and have you been underneath it to inspect for signs of leaks, even though they may not drip onto the ground? Also, how often do you change your oil, etc? Lots of guesses could be made, and will be made, but if you can provide a little history of the vehicle, it will be easier to narrow it down to the real cause.
My 2005 KJ with 116,000 miles uses a lot of oil, too. There's no sign of it being burned; no smoke from the tailpipe, and when I pulled the spark plugs they all looked normal. I do have the infamous oil pan gasket leak though; the area around the bottom of the engine is always wet,but it never really drips onto the ground because of the skid plate. The fact that replacing the gasket is a royal PITA on the KJ means that I'd rather just keep topping up the oil as needed.
Changed the oil 600 miles ago with 5-30. I don't have any records as I just bought the it. If it a leaked a quart to 600 miles I would think it would leave the underside coated or even the back glass speckled.
99 Green TJ SE
3" Full Traction Lift
4.88's, 33" MT's My Jeep
It should at that rate. May be burning it. You can't monitor your tailpipe all the time while you drive, your vehicle can burn oil and you just do not see it. Could have stuck or gummed up oil control rings due to mileage. Engine flush would help with that followed by an oil treatment. You also may want to look at your pcv valve, as it can stop blocking oil and allow your intake to suck vast quantities in. It's on the oil filler neck.
Revving the engine in a garage isn't a test that your engine isn't burning oil. It just means you didn't see smoke. Remember Star Trek, when you rule out all known possibilities, whatever left, no matter how improbable must be probable. If you aren't leaking oil, and its disappearing from the crankcase, aside from aliens coming down to earth and using a transporter to beam out your oil, its going out the tailpipe. You lack the oil cooler interface with engine coolant, so that rules that out.
You may be safe with saying no on valve seals, but you have oil rings, which is where I suspect your problem lies. Ford had plenty of issues with this, and partly why they started recommending their motorcraft spec'd 5-20 for a number of engines prior to 2001 to fix issues. Key word is the oil that meets motorcraft specs. You'll see it on synthetic bottles, not dino.