I’m thinking about renting my vehicle out on sites like Turo, but worried renters would put the cheapest gas in it instead of premium gas, if they always put in regular 87 fuel, would it damage the car?

 

It wouldn't hurt it, the ECU will just pull timing. I have a tuned F-Type and my tuner let me know that oftentimes summer blend gas actually falls short of rated octane ratings, and most cars pull timing anyways.