Block heater
 

I've never had one before - but my 3.8 has a factory install as it was built for Ontario.

Do I hook it up all night, or just for an hour before I want to go somewhere?

I doubt I'll see lower than -10 C but I do like the idea of near enough instant heat from start up for my kids :)

You'll probably never need to use it. They consume a lot of electricity. Since you say you never had one before, then don't worry about using this one. Just do what you always have done. Frequently, my temp goes below -20°c and I have never used the heater on my gas engine vehicles. However when ever the temp gets below 0°c, I need to plug in my diesel vehicles