Good day
Our 05 Suburban with 5.3l has about 250k miles and runs fine. Historically I rarely needed to add oil between changes. In the last 6 months, we get a big blue puff at most start ups and I an adding 1-2 quarts every 3-5 weeks. Seems like quite a sudden change vs slow wear and tear. So:
1. No test, what's your 1st guess
2. Tests to diagnose
This is my wife's DD and our trusted mechanic does all the routine care. He tried some additive 2 months ago; no change. He kind of suggested a crate motor as a fix.
Thanks in advance for your suggestions!
Red

 

so he want to replace the motor for a little oil burning??? try replacing the mechanic. worst case in my mind is gummed up o-rings but take a look here
https://chevroletforum.com/forum/gen...ing-oil-19313/

 

So just to quantify, 1400 miles about half on the highway, needed 2 quarts today.
Surprised I didn't get more responses/suggestions.
So how about if I ask "What would you do if this was your rig?"

 

check for leaks

 

No leaks, clean parking spot & clean motor. Again, see a big blue puff at majority of motor starts , but not all of them. After the puffs started, the oil consumption followed.

 

Like Irish posted, you want to look at restrictions in crankcase ventilation, ie. PCV valve and hoses.
Other than that you're looking at worn valves or pistons. I see no reason why a ring can't break or seal can't fail suddenly. Do a compression test to be sure.