35 gas-driven passenger cars, 7 significant French models in 6 geographical areas, have been studied under actual conditions. Vehicles were fitted with on-board data acquisition systems and sensors allowing to measure at second time intervals, the car speed, the engine speed, the throttle position, the intake manifold depression, the fuel consumption, the engine water and oil temperatures, the intake air temperature, and the use of choke, headlamps, rear-window heater and electrically operated cooling systems fan.The method used is described and some aspects of actual car uses by their driver(s), over a total of 23,000 kilometers traveled and 580 hours of vehicle running, are analysed : vehicle daily uses : rates, durations, distances travelled ; travel characteristics : durations, lengths, speeds, stops numbers ; engine running conditions : running ranges, engine speeds, thermal conditions, consumptions, and the uses of the choke, the gears and the auxiliary equipment.A mean of 5,5 car uses per day is observed, with significant differences between drivers or areas. A great number of short-length travels should be noted : 26 of the travels do not exceed 1 kilometer, 52 are less than 3 kilometers.The average speed over all the study is about 40 km/h. 90 % of the trip duration is traveled at a speed less than 90 km/h, covering 72 % of the distance.Engine speeds are not very high: 90 % of the duration at a speed less than 3000 rev/mn. Around one trip out of two is started by means of the manual choke, and 40 % of the distance traveled are needed to warm up the engine (water temperature less than 80° C).