Insure your own vehicle by the employer?!

Hello dear forum members! I hope you can help me. I have a T5 and wanted to sell it. I like the car so much, however, that I would like to keep it. Now the following thought came to me, which I have already discussed briefly with my boss. I work in the youth aid, with a self-employed little private carrier. Now my thought was whether I can use my car as a duty car. The advantage: I could use my car as a service car. T5 and my boss wouldn’t have to buy an extra car for our group. Is there any way that he “rents” the car from me? So I get a certain amount of money from him monthly for the use of my car, or he pays me the gasoline, or he insurances the car, or or what?! Sure, I can calculate all trips over the mileage of 30 cents… But that’s too cumbersome for both sides and he asked me to take care of whether I could take care of it. There are not also other possibilities from which we both profit. Would be very grateful about thought impulses! My previous web researches have unfortunately hardly helped me so far. Dear greetings, Kay