Here is a link to a thread on another forum discussing issues with contaminated WVO. The main point of this thread is not to diss WVO, but rather to know what you are getting. It seems that some people collect WVO with some harsh cleaning chemicals improperly disposed in the oil. The result is injector failures in trucks running contaminated WVO or even home-brewed bio. The moral of the story is to talk to the people who are supplying your oil, and coach them on proper disposal methods to ensure your oil isn't tainted.

Injector issues from contaiminated oil. - Powerstroke Nation

Just thought I would pass this info along to WVO enthusiasts as a "heads up", just in case someone isn't aware of this potential issue.