I have a 2010 Honda CRV with 168k today. Had it since 20k miles and have always used synthetic with religious 5k oil changes. When I hit about 100k, CRV used about a quart every 1500-1800 miles. Since the engine always was super quiet I never did the valave adjustment at 100k. But at 166k I decided I should check the clearances. I also decided I should check the PCV valve which was never replaced. The PCV still had a rattle but I decided to change it. The valves on the other hand showed all the intake clearances were to spec BUT all the exhaust valves checked about .008, and they should be about .012 so they were too tight. I readjusted them to .012 and the car now is a little bit noisier. HOWEVER my oil usage appears to have almost stopped!!! After about 1200 miles since the adjustment and change of PCV I have used NO oil!!!! Great but why the difference??????
Your PCV system was probably allowing oil to be sucked into the engine.
Most people don't realize the importance of the pcv valve. I learned a long time ago that every time I do an oil and filter change, I replace the pcv valve too. It makes quite a difference as you have found out, and it's probably the least expensive part on the car.
Crazy! Was only about $13 I beleive. AMAZING