I've never changed oil in a rental, but I've had to add oil to about half of them. Most recent and one of the worst ones was a Buick Envision with 5000 miles on it (still on factory fill), and it was well over a quart low. Barely had anything on the dipstick. It got a quart from my used oil bucket (which put it back halfway between add and full), and that was it.
On the eve of the eclipse in 2017, I went out to the airport to pick up a rental that I'd reserved, and the only thing that they had was a Traverse at 3% oil life remaining. I wasn't too terribly upset about it being a Traverse, as I'd reserved a mid-sized car. They were out of cars because everyone was headed south to chase the eclipse. I made sure it was full and took off.
Once it hit 0%, it went into nag mode... throwing messages and setting off the chime. So, I reset the OLM to shut it up. National was well aware that it needed service (I was told about it at the desk when they handed me the keys), so I wasn't doing anything that would keep it from getting serviced.
Had a 2023 or 2024 Toyota Tacoma that the OLM went off while I was renting it, and it disabled a lot of the functionality on the instrument cluster once it was unhappy. The instrument cluster went into some sort of "dumb down" mode. I hated everything about that truck, and cannot understand the following that those Tacomas have. The roominess and comfort of a Corolla, with the fuel economy of a Tundra, and a transmission that never knew what gear it was in.