My friend depends on my car to get around?
Talking's the only way, and in that conversation, be honest. It's very common for the person who has the car to become the convenient lift, as though, somehow, the person without the vehicle has some kind of entitlement to lifts on demand. Think of the kindest way in which you can say it, because if you do that and offence is taken, you'll have done the best you can. If it all goes badly you just have to accept that your friend has been partially using you as a convenience. The conversation should go something like: "I need to talk to you about the situation with lifts to work. Just lately I've been getting really overtired from having to get up so early and go out of my way to pick you up, and I hate this, but I'm going to have to stop doing it. I hope that you'll understand". That's all. Nothing long winded or untrue. You can't predict the reaction, unfortunately, but stay firm because the object is to get off this merry-go-round you're on, that you really can't continue with.