The dealer's selling a car, not geeking out on cross-brand engine detail differences! 
It shouldn't be too much to expect a certain amount of product knowledge from a salesman surely? Most car salesmen that I have dealt with have very little enthusiasm about the cars they sell. They may as well be selling a block of cheese. All they seem to want to do is tuck you up into a finance package that would earn them the most commission.
When I bought my Passat, I went in and sat down to begin my negotiations. I had nothing to part exchange and cash (debit card) to pay with. It was a case of, You've got the car, I've got the money, lets have a deal. The salesman seemed completely out of his depth when faced with such a simple proposition.
