That trick works good.  We don't usually need it until it's like -20F but it would help with the heater.  I don't think it's a "city person" thing, it's more where you live.  When we fill anti-freeze we will use one gallon of 50/50 and one of strait anti-freeze so you end up with around a 70/30 mix.  50/50 will slush in the radiator up if it's around -29 with the wind blowing.  Then you overheat, which seems odd .