hatchetman wrote:
It was pretty solid. Temp got down to 14 degrees F. What is the temp at which it will thaw/freeze?

The answer is "it depends." I don't think that FFA content is highly correlated with gel point, but certainly the feed stock and whether it is hydrogenated or not will. Unhydrogenated canola or soy should be pretty good, and should thaw again around freezing. But if you use WVO to make biodiesel, you don't just have veggie oil: there's probably animal tallow in there that freezes at higher temps.
If you want to be safe, run at B50 max when it's cold, leave room in your fuel tank to add (preferably warmed) kerosene or petrodiesel if your B50 samples gel, or keep the rig in a heated garage.