Car stopped using oil (sort of)

Ring finally came unstuck?

PCV stopped working or started working right?

My thought exactly. If the vehicle had infrequent oil changes prior to purchase it might have had a stuck ring and restarting a proper maintenance schedule and/or using higher quality oil than the PO unstuck it.

nate

used a little more than one quart per fill-up (300 miles ±). Have a spare low mileage (120,000 miles) wreck on hand, and meant to change engines if things got worse, or if I couldn't pass smog check.

I can go about 3 tankfuls (1000 miles ±) before I have to top off the oil. Not quite a quart.

leak, or whatever contributed to the oil consumption. Any ideas? Not complaining!

It wasn't entirely blowby due to wear. Something was probably sticking and not moving like it should have. PCV valve, piston rings (rotation), etc and so on. Once it got better care stuff started moving again like it was supposed to or closer to it.