My point was that WVO is an unknown feed stock that could vary considerably (it is a waste product), there would be no way of ensuring it's quality without constant testing to ensure there were no soluble contaminates (salts, sugars, etc.) left in the fuel. I assume that a producer would test every batch of feed stock prior to the expense of processing it to avoid waste.

I don't know what people produce in their garages, but I certainly wouldn't touch it without seeing the test results first.