Tallow is to beef as lard is to pork.

Many of the large turbodiesels, as in ships and generation plants, heat the bunker fuel oil simply to pump it. The same could be said of diesel fuel when temperatures reach 20 below Fahrenheit. Biodiesel depending on the original fats can solidify at relatively high temperatures and we all know you can't pump a solid let alone vaporize it. http://en.wikipedia.org/wiki/Biodiesel#Gelling

Lubrication. We did discuss previously that the fuel must be evaporated from the fuel mixture for the oil to provide proper lubrication. This is why viscosity is so important for plain bearing engines. Not so much at the crank because of the high surface speeds but more so at the conrod and especially the top end where there is very little surface velocity. The problem of vaporizing the fuel is the same reason we will never have a single component fuel that will properly lubricate the engine and burn as a fuel. If biodiesel with a viscosity of 4-6cSt at room temperature could lubricate an engine why would engine manufactures be using oils with viscosities 2-5 times that at 100C? I've never seen a spec for viscosity of biodiesel at 100C. I've only seen one published spec for autoignition temperature for biodiesel. The vapor pressure is low and flash point is pretty high for biodiesel meaning it will be hard to vaporize.

My four stroke engines have no issues with lubricant dilution running etherless fuels. There is plenty of oil in the crankcase whenever I check. While I have never analyzed it, it looks like mostly oil. Should try distilling the oil from the crankcase, but with such a small amount I don't know that household techniques would give much of an answer.

Andy, I keep posting the same reasons as to why your approach will be tough if not impossible. You keep telling me "what if?" There is always what if. But right now you have to prove to us in real life how "what if" is going to work before I take it very seriously. What if is great when you can say look at this.