Re: Personal Cheque or not, it seems to be based on the type of car. Paradoxically, the higher the price of the car, the less it needs to be a bank or certified cheque!
My Hondas: certified cheques all
My Lexuses and Porsche: personal cheques
For my first Lexus purchase, the Lexus dealer actually scoffed at the suggestion of me providing a certified cheque.