[Normal_gaussian]

My car costs me about the same as my groceries over the same period of time; they are very comparable in price. As for sales - buying in season and buying in bulk saves huge amounts of money, a larger %age than I expect to get off a special deal on a car.

[marcosdumay]

Closely controlling all of your grocery prices costs way more labor than closely controlling all of your car prices.

That said, I do adjust the amount I buy from groceries based on the current price. It's a cheap (in labor) way to save on them, but has lower gains than actively searching for deals.