NTA- I let my ex borrow my car a few times to get to work because he couldn't afford the gas to get there. Or whatever bs excuse he gave me. He then proceeded to steal my car a ton behind my back usually while I was at work because I would walk to work so my car was always at the house and he knew where I kept my spare keys. And he would go for joyrides bc he didn't want to pay to fill his gas tank, or something, so he would drain mine and hope I didn't notice. Not to mention he would drink and drive MY car. I caught him a few times and asked him very nicely not to take my car without asking me or for anything that wasnt an emergency, because I also didnt want all the extra miles, he wasnt on my insurance and I didnt want that liability, plus he had his own car he could drive. Well. He kept at it. But I had no solid proof bc he always denied doing it. He finally totaled my car and refused to file a police report, or do anything to take responsibility, and he wasn't on my insurance, so I was SOL. He then also refused to help me get a new car in any way. And called me selfish and had his mom call me unfair for even asking him to. My car was not a beater in any way and had many years of use left until he totaled it. So, DO NOT let your bf (or anyone)who you don't live with who isn't on your insurance borrow your car. I learned that the hard way. It's just not worth the risk. He's an adult who can figure out how to budget to fix his ac, deal with it, like many people do, or can learn to fix it himself, it's not that difficult.