When my insurance and finance companies talk about GAP insurance they mean the difference between 'fair market value' and 'outstanding loan balance'. It's to protect you from making payments on a car that's been destroyed if the settlement doesn't cover the loan balance.

A typical settlement would be some depreciated value which wouldn't necessarily be enough to simply go buy another car A with mileage B like you just lost, especially if you are subject to big tax and registration fees. There's always a lot of discussion on this board like, 'ooh, ooh, I pay $10/month less than you for insurance on my RX-8 :-P' but a stingy insurance company may settle a loss for thousands less than the amount you'd need to go buy the same car (used with same mileage) on a dealer lot with your settlement check.

I had a mechanical odometer in my Pontiac Sunfire that burned. There wasn't anything left to analyze (or worth analyzing). There might have been some steel core to it that could be analyzed like CSI, but in addition to the numbers melting off, everything around the dash was melted and charred so you'd have to use a chainsaw to get it all apart.

I'd had new tires installed on the Sunfire about 6 weeks prior to the loss and the tire center had my mileage on the service record. Rather than negotiate some 'fair' final mileage based on my average weekly driving habits they just used that 6-week-old figure on the service record I faxed to them.