As a CTD reference:
Came across a post by a retired engineer in Edmonton, AB runs a diesel-powered Dodge 24/7/365 in the oilfield:
. . I keep it plugged in when at home - start up temp 104 F
or 140F when on the road with the Espar heater running
EDIT:
And later today came across this (a little farther removed from topic):
http://en.wikipedia.org/wiki/Weather_Eye
AMC Weather Eye
.