I've owned diesels all my life . My cummins starts right up at 0F , although two years ago it was real cold , and not much you can do when the fuel gels , additives and all . I wouldn't heat a shop unless your gonna work In it all day , it will get expensive . Natural gas is probably the cheapest route here , 2 of my friends have geothermal which is really efficient , but a major upfront cost .
I love my area , but I hate the cold ! Our first snow is happening as I type . Lake effect coming in , there saying ski country 2-3 feet . I say just hide inside for 2-3 months lol. Hence I'm working in the basement .....