My KJ (3.7 4wd) goes through quite a bit of oil, around 1 quart per 800-900 miles.
I only use 5W30 Mobil 1 full synthetic high mileage oil, and change it every 4,000 miles.
As far as I can tell, there are no leaks anywhere. Valve cover gaskets are in good shape, and I just replaced the...