For these converted diesel vehicles with the dual tanks--do they have to switch back to diesel before shutting off their engines? I'm just wondering, if you turned off your engine while it was running cooking oil, and it was cold, it would seem that the oil would really gum up the engine when it eventually gels.

But back to the generator, I don't see any convenient way to switch between diesel and cooking oil except for warming it up on diesel and then adding the cooking oil to the tank. And then what? Adding diesel back again when you're getting near to shutting it down? That sounds like a pain, and when you shut off your generator is not always something you can plan ahead for.