a personal loan has no collateral against it(no vehicle lean), hence the higher interest. i def would not take over his personal loan. if anything go get ur own and if you have good credit itll prolly be less interest than his is.
i only take personal loans on cars if they are a small amount (say like under 7 gs) and i know i am going to pay them off quickly. take out the max term to get ur monthly real low, then double or triple the payment and shell be paid in no time.