Well, these engines might be easy enough for one of us to start, but maybe not if the spouse needs to start it while your away for periods of time in the winter, and the engine has no electric starter yet. In addition to that, the engine would stay warmed up if it was simply "idled".
I disagree on the fuel consumption. In spite of a little more blow by, I think the difference would be dramatic. You would definitely want to use an engine with an oil pump though. At slower speeds, combustion would have much longer to complete. So even if compression was slower and ignition was a little lazy, these effects would be canceled out by the longer stroke time giving combustion extra time to do the same job. I doubt there would be any injector dribble with the type used on these engines, even at ultra slow RPM. I think we are largely in the territory of empirical knowledge here, where the only way to know for sure is to test things out in a well designed experiment. Using full synthetic non-detergent diesel crankcase oil would help a lot at slow speeds as well. Does anyone make such an oil! Probably not.
I specified pump diesel as a baseline comparison fuel. It is true that biodiesel, being an ester with methanol, would have a higher cetane and burn better, but with lower BTU's per gallon. WMO and WVO would not be the same unless mixed with generous amounts of pump diesel or Bio. I always thought it was funny how people would get into making biodiesel to get away from using petroleum oil based products. They didn't realize that all of that methanol they were using in the biodiesel manufacturing process was............ a by-product of oil refining! Sometimes it's made from natural gas reforming. I think the oil Barron's were getting excellent laughs out of that, and were probably actually promoting the use of biodiesel! My late father was a chemical engineer who designed refineries nearly all of his life.
You would be surprised at what you can make diesel and/or gasoline from. The Germans had very little oil reserves during WWII, (except maybe from some nations they conquered) they made most of their liquid fuels from reforming coal. Their processes made far better diesel than gasoline. That might explain why most of their tanks ran on diesel, while most of our's ran on gasoline. Now days, it is theoretically possible to make gasoline, or diesel from almost every drop of a barrel of crude, although no refiner would ever do that due to the extreme costs. There are many installations currently making gasoline and/or diesel from natural gas. Very little fuel is "straight run" anymore.
This is a good time to work out these details. Next time the price of oil goes up, maybe 5 years or so from now, we'll all wish we had alternatives. I am suspicious that the next time the pricing of a barrel of crude goes viral, it will take on biblical pricing proportions. By then, I hope to be mostly solar. Of course, by then, the fed's will probably have figured out how to tax for the use of the sun as well.
