Carmax uses The Warranty Group for their warranty ...

Carmax uses The Warranty Group for their warranty claims and processes. TWG is one of the worst warranty agencies I've had to deal with and are the personification of "the man", "corporate America", and "crooks" which diminishes Carmax's credibility. Purchase if you have to from whomever is using TWG, most try to make it work. But after your purchase, you'll be on your own or up for a fight if you want to leverage the warranty or coverage they say you have. Best of luck!