High oil consumption should be investigated!
Apart from the obvious like engine wear the crankcase breather on earlier models (found on the passengers side valve cover) has a habit of rupturing its diaphragm and blowing oil into the induction tract.
The other can be oil carry over across the turbo. K&N filters when neglected or poorly serviced create a high depression in the induction tract which doesn't help!
I have one in the shop that came from another shop who flung their hands up in surrender!
Even tore off the cat and hollowed it out! And with a no code condition!
Clouds of blue and white & MORE blue smoke! Even fogged out the missus in the back office! Got a cussing!
Base lining the engine (which should have been done in the first place) I found the turbo impeller and shaft sheered off! Crankcase oil was pouring into the turbo snail housing and into the engine where it was being burnt--quite spectacular! Emptied the crankcase it did!
Retired the truck to a stall for repair with the missus still cussing about the stink in the office!
She smells acrid diesel, I smell green money
Dennis