My JM284 lives in an uninsulated, three sided steel shed. When it got to -10 around here (northern Nevada) last week, he was totally unimpressed. I installed a 250 watt Model 16 Wolverine heater, and at zero outside he fired right up, even without using the decompression lever (I know, Greg, but had to test it!). I do put a tarp over the hood, extending down past the engine, as an additional aid in keeping the engine/fuel warm with the Wolverine. Also, I burn number one diesel, and add about 1.5 ounces of Power Service to each 5 gallons.