1) agreed. 2) I guess I was splitting hairs, or arguing a different point. The detergents/additives that are added cause a change in viscosity, sure, but that's not why they pose a problem. It's whether or not they are skin safe, as you mentioned, and can saponify, that we care about. And most of the oils in motor oil are not esters, will not saponify. That's very interesting about the biodeisel being used for soap making! Were they ugly looking? What did they smell like? No fragrance was used?