 In addition to claims of cars that run exclusively on water, there have also been claims that burning hydrogen or oxyhydrogen together with petrol or diesel increases mileage and efficiency; these claims are debated.A number of websites promote the use of oxyhydrogen, also called "HHO", selling plans for do-it-yourself electrolysers or kits with the promise of large improvements in fuel efficiency.According to a spokesman for the American Automobile Association, "All of these devices look like they could probably work for you, but let me tell you they don't".