Nitro Dude
Hauler Driver and Cylinder Head Maintenance
The older trucks use to have a grill cover with a zipper on it that attached to the grill and when you were parked in extreme cold weather you would zip them up so the water temp would stay hot enough to put heat out. You had to be careful not to forget to unzip it before driving because it would overheat your engine if you did. I don't know if they still use them on the newer trucks or not. I know I haven't used one since the 80's.