Sometimes when I have known oil burners in the shop, I use a heavier weight and don't even tell the owner. Examples include most Subarus (esp FBs that call out 0W20) and old, tired V8s.
I have one guy who has obvious, diagnosable OCD (picture Tweak from South Park) with an '11 Forester. He brings his own oil and blabs while I change it. He simply CANNOT bring himself to run anything other than 0W20 because that's what the cap says. He uses a quart every 900 to 1000 miles, even with only 80k on the motor.