I hear that MPG is worse before your truck warms up to normal operating temp. I live in a cold climate and frequently only make short 10 minute trips to & from (live & work in a small town). So I'm pretty much driving my truck cold much of the time.
My question is has anyone checked to see what an engine block heater does for winter gas mileage? Because theoretically, it should improve it .. especially if you do a lot of cold start short trips like I do.