Cheating Fiance - Separation and Car Repayments

My fiancé (de facto) and I have separated after he was cheating on me with his ex partner for the last three months. We recently purchased a brand new car together for me, that is financed in his name only but the dealership/ownership papers are in both names. He has been making the repayments, and I would like to know if I keep the vehicle and he agrees to still pay half of the repayments, can he legally in six or twelve months change his mind and just come and take the car from me?