I don't use any block heater, oil heater or any other gadget.
The car sleeps in my ''blue sky Moonlit garage'' (i.e: outside) and all I use to start it is my remote starter button.
Temperature went down to - 36 last week for a almost a week and I did not have any start-up problems. it starts in about 2 seconds each time.
What could have happened for your car not starting is probably related to the gasoline you used. In cold weather, the RVP (Reid Vapor Pressure) is adjusted to make gasoline more volatile in very cold weather. if you fueled in Conn, you gasoline was propably not treated for the -20 temperature.