A more economical heater would be to use a small silicone rubber heater pad to keep the engine at a startable temperature. Get some black hi-temp RTV sealant and glue it to the side of the oil pan. I always glue mine to the side of the pan in case I have to use a weed burner or propane stove under the oil pan. They come in everything from 5W to 750W.
Amazon silicone heater padsOn my Ford diesel I have them on the oil pan, under the two batteries and the transmission pan. I only use the one on the engine oil pan for normal winter weather in Anchorage, but if I'm going up north and it's really cold, I'll use all of them.
Bill
