My experience with severe cold starts with a diesel is only with Case tractors years ago. We owned two case 300 series diesels that would start fine unless it was below 0f. Then they would start after a few tries after pumping so much raw fuel smoke out the pipe I expected the barn to explode when they did fire up. My 300d has been in temps as low as 20f and started with no problem as long as the plugs were working. Colder than that who knows, I hope I don't have to find out