Nanotechnology company Cerulean International is going to try to do to England what it's done to Hong Kong: cut fuel consumption in city buses. Cerulean is a subsidiary of the British nanomaterials company Oxonica. Small Times reported back in 2001 that the company would test its nanoparticle fuel additive on Hong Kong's city buses.
Apparently, the test was a success, although I cannot immediately find any independent confirmation of it. The company says the trial "demonstrated up to 12 percent reduction in fuel consumption," but this June document (PDF, 205 KB) from the World Bank, which helps fund the company through its Clean Air Initiative for Asian Cities, says Cerulean is "in the process of documenting all of the testing carried out."
The fuel additive is called Envirox, an oxidation catalyst that helps fuel burn cleaner. It's not your father's oxidation catalyst, though, because it doesn't sink to the bottom of your tank and come out as exhaust gunk. That's where the "nano" comes in. As Small Times correspondent Genevieve Oger reported back in 2001, the additive has been chopped down to 5 or 10 nanometers and coated with a fatty acid – small enough to mix with the fuel but big enough to be effective.
British bus company Stagecoach UK has volunteered 1,000 of its buses to go through the full nano treatment and see what happens.