It might depend on what kind of oil you are using. When I use Mobil 1, my truck will burn one full quart every 3,000 miles. However when I use Amsoil, I MAY burn 1/2 a quart over 5,000 miles. So thats longer distance with less oil burn. What kind of oil are you running?

......I too have noticed zero smoke.

 

was running Valvoline 5-30.... then moved to 10-40....
I still have some pretty noticeable valve train noise. (I have yet to remove the valve covers and check rockers, etc.) Today I changed the oil and used Castroil 20-50... Hoping to maybe stiffen the pressure up a bit and relieve some valve noise....
Usage doesnt seem to be so bad... hadnt put any oil in recently and drained a lil over 5.5 qts out...
Is the heavier oil going to be a problem... 155k miles...
Also.. since selling the Duramax, I have 3 - 1 gal jugs of Rotella 15-40 left in the cabinet.
Would there be a difference (problem) in using the Rotella next oil change versus conventional?... what is the difference anyway?

 

Something similar happened to me a few years ago when i first got my truck. Changed the oil and went for a drive, while on the highway a lifter started ticking like it was gonna fall apart. Drove it with that engine for a while cause it would only do it on the highway occasionally, then found a replacement to put in.

 

i would pull the valve covers and make sure your rockers are all tight and the springs are good. also pull a couple plugs and check for oil. if they are dry then you are more than likely consuming oil via the pcv system which is pretty common. also noise at cold startup that goes away when warm sounds like piston slap which is also normal. you could always see if you can catch it on a vidoe and post it on here for us....