My WRX stays in the mountains here in CO frequently where it can get pretty cold. When the temps drop below 0 or so at night, in the morning the car can be tough to start. You really gotta just keep trying in short bursts for awhile and then eventually work into giving it gas. I've heard of people using some kind of heating element to keep the oil or coolant warm at night. Is this a widely accepted practice? Is there any reason not to do this?