A couple of things here. In order to deduct mileage you need to claim a business and deduct it there. SO that's not going to happen. Here's where it gets a little sticky. In order for him to deduct mileage the car has to be invested in by him (by that I mean he has to own it SO that's not going to happen). If he were paying you on a lease basis you could claim it but you'd still need to claim a business. Better to let sleeping dogs lie.
