On this issue, Dr. Monzer Kahf, a prominent economist and counselor, said that ‘trading a used car for a new one is permissible, and the price matter of it is subject to negotiation and consent. It is an issue that sharia does not interfere in except from the point of view of monopolistic power. It is haram to exercise a monopolistic power that ends up unjustly raising/lowering the price on the weak party being a buyer or a seller.
The Hadith about date is correct but there is no analogy between date and cars. Date is a cash crop that is a general staple food item at that time in Arabia the rule applies to similar cash crops. On the other hand we also have correct Sayings about exchanging one camel for two.