Commercial vehicle fuel economy — The correlation between aerodynamic drag and fuel consumption of a typical truck☆

Abstract In a programme designed to demonstrate the benefits of reducing the aerodynamic drag of commercial vehicles a number of tests were made in the MIRA 7.9 m × 4.4 m wind tunnel using a full-scale truck fitted with a number of proprietary drag-reducing devices. Then, to establish a relationship between the indicated drag reduction and fuel savings, steady-speed fuel consumption measurements were made on a test track using the vehicle fitted with many of the devices tested earlier in the wind tunnel. The highest measured reduction in drag coefficient, 36%, which was achieved with two devices used together, resulted in a fuel saving of 16% at a steady speed of 80 km h −1 and of 13% at a constant 50 km h −1 . Further measurements, made on a 365 km road test route, and using one of the more efficient single devices, indicated a fuel saving of 13.2% under normal road conditions. A good correlation was established between the wind-tunnel measurements of aerodynamic drag and the steady-speed fuel consumption measurements.