As I understand, the "fail safe" thermostats jam open when they overheat, by design. From then on, you have an always open "no T-stat" and the resulting poor mileage and extra engine wear. I wouldn't use one.
Not true.... if their is a failure it does stay in the OPEN position instead of slamming shut to OVERHEAT the motor and fry it.... open will allow you to make it where your going and change it instead of calling the tow truck...