Scam at DFW?
 

I had reserved a full size car at DFW. The agent asked me if I wanted to pay an daily upgrade fee to go to a minivan, PT cruiser, or Concorde. I explained that I wanted only the full size. He then said they were out of fullsize cars and would give me a free upgrade to a minivan. I explained I did not a minivan or PT cruiser. These were not acceptable for the passengers I anticipated. He basically said I had no choice and had to take the minivan. I said again no minivans. I asked for the Concorde and finally got it for no upgrade fee. I think it is very inappropriate to try and scam people into paying an upgrade fee when in fact they are going to be upgraded anyway whether they wanted to be or not.

This is common among many rental companies, and I wouldn't call it a scam. If someone is willing to pay for the upgrade, so be it. People pay different prices for things all the time based on their negotiating ability and their knowledge (or lack thereof) of how the industry works.

A savvy traveller wouldn't pay for an upgrade unless they absolutely needed it.