plugged in

All. I performed a very unscientific test of plugging in the engine block heater and not plugging it in for two nights in a row. The overnight temps were in the low twenties and almost identical. Just wanted to throw some fuel and perspective on the debate. :|

Any insight would help, please. I have a 03 6.0 :icon_ford: Ex, as the weather got colder (<40 degrees) the truck would not start. I plugged the block heater in 4 hours or more and after a few tries (could hear the flywheel engage and the teanny temp rose) it would finally crank over. Once the...