Okay, I know the manual says to use the engine coolant heater when temps are around zero. I babied our old 96 and plugged it in when temps were around 30 above zero and under. It did help it start easier. I now have 2006 Silverado Duramax LB7 and was wondering if it would hurt to plug the truck in when temps are in the 20s or 30s above zero. Thanks for reading.