Vegetable oils are thick when cold and can clog the system. This is why VPS makes only dual-fuel systems. Until big refineries start working with vegetable oil and figure out how to produce less-viscous versions, you'll need to run a dual-fuel system at least so you can "hose out" your fuel system before shutting down your diesel. Cold vegetable oil in your fuel lines will eventually clog your injectors and other parts of the system. This is why you always need to start up and shut down your diesel vehicle on petroleum diesel. VPS runs a T-fitting off a main cooling hose and runs the line back to their inboard tank heater to warm the veggy oil in the tank to a workable temperature so you can switch over to warmed veggy oil once the engine is up and running. The veggy oil system intersects with the factory fuel system underneath the truck, instead of running parallel fuel lines all the way to the engine.