The demands placed on vehicles are constantly increasing. European legislation has forced commercial vehicle manufacturers to develop ever more powerful and dynamic engines with low fuel consumption. With the appearance of exhaust gas standards, truck manufacturers realized that it was necessary to improve the fuel supply system so that the combustion process was more efficient. To achieve this the fuel injected into the cylinders had to be finer in order to mix more easily with air. High-pressure unit injection systems have proved to be a good and reliable solution. They are also relatively cheap to produce and less prone to fuel contamination. Many years and millions of failure-free kilometers traveled on unit injectors effectively distracted some users and producers from the Common Rail system. Exhaust gas standards and increasing consumer expectations forced manufacturers to take another step in their development, i.e. the need for more precise fuel injection control. The injectors had to run faster in order to carry out the initiation dose, the actual injection and the extra injection. All these modifications make diesel engines in commercial vehicles such as tractor units much more powerful. They also allow for cooperation with aftermarket dual-fuel CNG-ON and LPG-ON installations. Dual-fuel solutions are perhaps another step towards reducing emissions, and thanks to reduced tolls, they are becoming a real alternative to conventional fuel-powered tractor units. This work focuses on the structure of the truck tractor market in terms of selecting cars used for the use of a non-factory dual-fuel CNG-ON installation.