I maxed my 3rd car yesterday.
I will try to max one car each day and then do one NG+ playthrough of Starfield. 2 grindy games, i still have to do like 4-5 NG+ in SF. Then all my powers are at ten and i can finally stay in my permanent NG+.
Today i will max the Ford GT that the player wins in one of the series. That will be my 3rd Ford, so 2 more to go after that one, for the max discount for all Fords.