I older trucks you can't run pure biodiesel because it is incompatable with rubber. Newer vehicles, however, can run on B100 with no problems. Let's keep in mind though that biodiesel and vegetable oil are not exactly the same thing. If you want to run straight vegetable oil you would need to modify your engine. I also would not recommend doing this because most of the research that I've seen shows that it is very hard on the injection system.

You can certianly run B20 with no problems (as shown in the picture from your link). From what I've heard, most people report that their engine runs smoother and quieter on biodiesel.