Try this,

(I am assuming he is responsible for 16, and isn't getting it for joy riding or drinking with his pals, showing off, etc... They are really nice vehicles for the money).

Make a legal binding contract between you and your son. The contract will include his portion of gas/insurance/maintenance that he must pay to maintain the car. His agreement to be responsible with the car, not to get tickets, and to use it wisely... etc etc... you get the point. Include some sort of penalty clause for 1st ticket, 2nd ticket, wrecks... etc... Incur penalties and a paternal "repo" if things get out of hand and responsibility wanes...

You sign, he signs. Monitor... adjust agreement to real in son or give more lee-way over time... You never know until you try ... Depends upon your trust level with the kid... You know his history, we all don't. So I personally can't recommend anything beyond that unless I meet with the kid and get to know him...

And, you can adopt me at any point, if your son fails in his commitment to do drive responsibly... I will take real good care of that thing, really... Contact me via PM if you want my address to send the adoption paperwork.