The ICCT commissioned the Institute for Internal Combustion Engines and Thermodynamics of the Graz University of Technology (TU Graz) to conduct track and chassis dynamometer testing to determine the aerodynamic drag, pollutant emissions, and fuel consumption of three European heavy-duty vehicles. Publicly available literature on the fuel consumption or European trucks is scarce. The vehicle testing commissioned by the ICCT seeks to fill this knowledge gap by testing three trucks over a wide set of driving cycles and payloads in a controlled laboratory environment and following strict test procedures. The results of this study are relevant for informing the fuel consumption of trucks being sold today, and for understanding the differences between average and best-performing vehicles. The testing campaign identified a large fuel consumption difference between a typical tractor-trailer, representative of the EU fleet, and a best-in-class vehicle. Over the regulatory Long Haul cycle, the best-in-class tractor trailer consumed 29.9 l/100km. The typical tractor-trailer consumed 9% more fuel at 32.6 l/100km. The source of the measured difference in fuel consumption is the powertrain efficiency. While the best-in-class vehicle required 3% more energy at the wheel, it also had a powertrain 11% more efficient than the typical truck.