I’m living with my boyfriend of five years. Three years ago his daughter came to live with us. I’m the breadwinner, making nearly 10 times what he makes in a year, and so I’m heavily supporting our family.
We recently leased a car, when we had otherwise been relying on public transportation, Uber, and cabs. The car is completely in my name and on my credit, though his income was taken into account when we decided we had enough collectively to get a car. My boyfriend does not have a license nor does his under ‘driving-age’ daughter. When I talk about the car, I often call the car “my car” though I drive them wherever they need to go on most occasions. My boyfriend gets really defensive about me calling it “my car”. – which I think is mostly out of habit from when I had a car before, but could also be because I’m the only one that drives it, pays for it, and is ultimately responsible. Should I be more sensitive to this being a family car and calling it “our car”?
LemonVibe 
If it’s just this one little thing then call if our car around him, because I am sure you have bigger fish to fry with a teenage daughter, being the main provider and so on since you plan on continuing to stay with him.
However of you break up you don’t owe him didly since you are not married and therefore your car. It goes to you. You paid for it and all legal documents hold your name.
This is a wake up call however. Are you staying together since this bothers you? You are the only one who can answer that. I don’t actually need to know.
Simple solution. Just call it THE Car. No possessives.
After five years, you should either consider getting married and being an “us”, or breaking it off. If you already share a life together, make it official. If you want things to be separate still, consider that you need some time to work on your commitment issues. Or maybe he does, but it kind of sounds like you, since you know, you’re the one getting all hung up about the “my car” thing. If I was with someone for five years and shared my whole life with them, I’d certainly have no trouble calling ANYTHING in my life “our” thing, regardless of who paid for it. Our bed, our car, our dog, our cat, our computer. Don’t emasculate or lessen your dude because he couldn’t afford to buy a car. If the tables were turned, if he paid for it and you were a housewife, you know it’d be “our” car in a heartbeat.