An instrumented “chase” car was used to observe and record driving patterns for over 3,000 motorists in three different regions. How these motorists actually drove their cars was then compared to three standardized driving procedures used to evaluate fuels: the EPA's city and highway driving schedules used for emissions and fuel economy testing, the CRC E-15 Technique for Determination of Octane Number Requirements of Light-Duty Vehicles, and the CRC Cold Start and Driveaway Test Procedure used in fuel volatility work to evaluate vehicle driveability. All of these driving procedures were found to differ from the way motorists actually drove their cars. Accelerations are generally less rapid in the EPA cycles, and engine loading is lower than it is on the road in both the acceleration and cruise modes. Accelerations in the CRC E-15 technique were not consistent with the way motorists actually accelerate and the magnitude of the accelerations depended on the car being rated. In the CRC driveability cycle, some of the maneuvers were difficult to follow, resulting in poor repeatability of the accelerations.