The system I mentioned had a complete purge system built in, but vosa were not interestedPS Duel fuels are only allowed on vehicles if the red is used for operating a machine etc carried on the back and it has a separate tank for the white used for propulsion. You can’t just switch from red to white and vice versa without cleaning the whole fuel system down and also changing the taxation class of the vehicle, it will also bring into consideration other things such as tachometers and O licensing.