Burning Oil without Smoke?

near .5 million clicks on the '88, 4.0
'fill the oil, check the gas...'
no leaks visible - gotta be burn'n it
What needs replaced and how big of a job is it?

Thanks
XJHarry

How much oil is it burning? Can you ever see smoke (try going down a long hill in third gear, no throttle, and look for a cloud when you hit the gas again)? Can you see fouled plugs? How much oil is going into the air cleaner through the crankcase vent?

I'd start with a compression test. If it needs rings you're looking at a real rebuild. If it doesn't, perhaps it just needs valve seals.

I was always told 'smoke under acceleration, rings' 'smoke going downhill off gass, valve seals', 'if neither start looking for leaks'...