NOVELTY - The system (12) has an acceleration sensor (16) determining current acceleration of a vehicle (10). A fuel sensor (18) determines current fuel consumption rate of an internal combustion engine (24) of the vehicle. A processor (22) is coupled with a speed sensor (14), an acceleration sensor and the fuel sensor and operatively coupled with a display unit (20). The processor determines instantaneous fuel economy of the vehicle based on information obtained from the speed sensor, the acceleration sensor and the fuel sensor. The processor instructs the display unit to display the economy.    USE - System for calculating instantaneous fuel economy for a vehicle e.g. hybrid electric vehicle, battery electric vehicle, hydrogen fuel cell powered vehicle such as passenger saloon car. Can also be used for passenger car, van, minivan, motorcycle, lorry, bus, military vehicle, ground-based vehicle such as automobile, aircraft, water craft and spacecraft.    ADVANTAGE - The processor instructs the display unit to display elevating instantaneous fuel economy in increments that do not exceed predetermined amount so as to avoid cause of confusion to a driver and to enhance the driver's ability to correlate driving habits with impact on the fuel economy of the vehicle.    DETAILED DESCRIPTION - The display unit is selected from a group consisting of CRT display unit, flat panel display unit, LCD display unit, plasma display unit, electro-luminescent display unit, LED display unit, holographic display unit such as a Head Up Display unit, and Micro Mirror Device (MMD) display unit. The processor is a microprocessor. An INDEPENDENT CLAIM is also included for a method for calculating instantaneous fuel economy for a vehicle.    DESCRIPTION OF DRAWING(S) - The drawing shows a top view of a vehicle equipped with a system for calculating instantaneous fuel economy for a vehicle.    Vehicle (10)    System for calculating instantaneous fuel economy for vehicle (12)    Speed sensor (14)    Acceleration sensor (16)    Fuel sensor (18)    Display unit (20)    Processor (22)    Internal combustion engine (24)