I personally wouldn't do it based purely on financials. Every time you go to dealership or make a transaction there's a lot of financial 'friction'. The dealer has to make a profit so they sell at a bit higher and buy at a bit lower. And you have to pay for taxes, dealer fees, doc fees, pre purchase inspections, etc... If you add all of that up, it adds up.

From a purely financial perspective I make as few car transactions as possible. It's a different story if you just don't like your current car or whatever. But purely from dollars perspective I wouldn't