I was on one of the other diesel sites a couple of weeks ago reading about WVO in a truck that was getting Blackstone reports on the oil done on.

The report was showing ring errosion and the oil was getting stringy from the glycerin that made it past the rings.

I think WVO is a pay me now or pay me later kind of thing. Yes you will save money now, but in the end it is still gonna cost you to rebuild the engine before you should have to.
Also WVO is still untaxed fuel that you can be busted for running and is easy to detect just like red fuel is.
I also do not think any of the IDI motors had seals that are biodiesel proof if you run high percentages.