How should I approach my boss?

So a little over a month ago, my boss asks me into his office, and asks me how I like the bus system (I take the bus to work) I said I hated it jokingly. Then he said well I want to get you in a car, I will pay for the car payments and registration ect. I was so excited. Now it has been a month and I haven't heard a word about the car situation. Now it's been a big month, his son graduated, he has a lot of business deals going on ect. But now things are slowing down and Im wondering when the car situation is going to come up. Should I bring it up? If so, how do I approach him? Should I leave it alone? Please help.