The Duromax XP4400EH has a dual fuel system that operates on either standard gasoline or cleaner burning liquid propane which can more than double you generator’s run time. With the XP4400EH, operating on propane will not gum up or foul your generator’s carburetor and will give you quick, reliable starts every time. It only takes a few seconds to switch over from regular gas to propane and with the flexible line, you can easily hook up any size propane tank including the one from your barbeque. When the ambient temperature is under 40 degrees propane by nature contracts and the pressure within the cylinder is not powerful enough to push enough gas into the carburetor to START the engine. The solution to this is to start the engine on gasoline for a few minutes and then switch over to propane.