I've had slow cranks in Maine and wished I would have had a block heater. Yes it takes extreme temps to "Freeze" fluids but how well do they work when within 10-20 degrees of their freezing temps?! Probably not well at all and if you can install/afford a block heater it probably wont hurt a thing, hell, even keeping a block up to temp in 40 degree weather will help with cold starts.....