Studies show that cars use significantly more fuel per kilometre than suggested by official test ratings. This publication presents an analysis of the fuel efficiency gap and examines technologies available that could reduce that gap and improve fuel economy. It examines such areas as engine and transmission technologies, hybrid technologies, tyre inflation and technology, lubricants, and fuel-saving driver support devices.  Together, these technologies could improve average on-road fuel economy by 10% or more at low or modest cost.  Policies that could be used to encourage uptake of these technologies are also identified.