NOVELTY - The method involves determining actual ambient condition data in a geographical location. The actual ambient condition data is compared to stored historical ambient condition data for a given geographical location to create estimated ambient operating condition data. A determination is made whether the estimated ambient operating condition data is accurate within a predetermined range (68). Powertrain operation is modified when data of actual ambient condition differs from the historical ambient condition data by a predetermined amount.    USE - Method for operating a powertrain e.g. engine such as internal combustion engine, a fuel cell power plant, a hybrid electric vehicle powertrain and an electric motor, by comparing historical to actual ambient operating condition e.g. barometric pressure, temperature, altitude, air density, wind speed, wind direction, rainfall, powertrain speed, powertrain torque, fuel consumption, daylight hour, night hour, period of sunshine, period of overcast clouds, humidity, vehicle speed, road speed, vehicle travel direction, road condition and terrain configuration (all claimed), in a vehicle during travel.    ADVANTAGE - The method enables operating the powertrain based upon comparison of historical operating data and actual operating data and modifying the operation of the powertrain based upon predetermined difference between the historical operating data and the actual operating data, so that the powertrain is associated with an electronic control module (ECU) having access to historical data, thus comparing the historical operating data to the actual operating data effectively by modifying the operation of the powertrain in an easy manner based upon comparison during travel.    DETAILED DESCRIPTION - An INDEPENDENT CLAIM is also included for a computer-readable medium comprising a set of instructions for operating a powertrain.    DESCRIPTION OF DRAWING(S) - The drawing shows a flow chart illustrating a method for operating a powertrain.    Step for determining geographical location of vehicle (56)    Step for determining travel path or route of vehicle (58)    Step for determining ambient actual operating conditions along travel path or route (60)    Step for plotting ambient actual operating conditions around vehicle travel route (62)    Step for determining whether estimated ambient operating condition data is accurate within predetermined range (68)