-40 will freeze a vehicle quick as . So we have engine block heaters, oil pan heaters, heaters, and battery blankets. I also have a battery trickle charger hooked up. All of these heaters go into a 3 way plug. the male end of the 3 way comes out through your grill. We all carry winter extension cords, and most places have plug ins (poles with outlets on them). Both my job and meghans job have plug ins, All apartment buildings have plug ins in the parking lots. My house has outlets out by the garage, so I plug in there. The supermarkets dont have plug ins, so normally you just leave the car running while your there. Our bar doesnt have plug ins, so you either leave it running, or start it every once in a while. (Though if you are a regular and you need to leave your car plugged in overnight, there is a secret plug in the back) Many times tho, that plug has been taken already, so you run a 100 foot extenstion cord into the bar the next morning, and give it about 4 hours to warm up. this always turns out bad, because if you leave me in the bar for four hours, there is a good chance I'm going to be drunk again.
It might sound crazy lol, but it becomes second nature pretty quick. The male end of my plug came out of the cord last week, so nothing was heating up. For two days I left my truck running while I was at work lol.