In Milan itself you're probably a little limited in terms of cars/transport to:
i) National Science and Technology Museum (Via San Vittore)
ii) ATM Historic Archive (Via Ricasoli)
iii) Pirelli Historic Archive (Viale Sarca)
If you can go a little further afield there is the The Quattroruote Museum just south-east of Milan at Rozzano and the Zagato factory just north-west at Rho.
I don't know however if you can just 'drop in' to these or some kind of prior notification is needed ... worth doing a quick check first!
Hope it's nice and sunny where you are and you're having a lovely holiday!