2004 Ford Ranger fuel economy dropped overnight

My 2004 Ford Ranger fuel economy went from 17 mpg to 11 mpg overnight

for that to happen overnight someone siphoned gas out of your tank. checking your mileage one day and then the next without using it in between thats the only thing i can think off. or you have a gas leak

Have your driving habits changed? Beyond that, you might have a stuck thermostat.

Good point. Thanks.