Piston combustion engines used for propelling vehicles have a significantly harmful impact upon people’s living environment. As a result, for many years now the development of combustion engines has been to a large extent defined by growing legal ecological requirements. New constructional solutions are being introduced, the conditions of working processes in engine cylinders are being changed, new solutions are being implemented in fuel feeding systems, air intake systems and fumes exhaust. The composition of conventional fuel is being modified, alternative fuels are being sought for and new types of powering systems are being developed. This paper presents the comparison of selected efficiency and ecological indicators of two engines having the same construction, but different in the type of powering and the method of controlling the process of supplying fuel and air into cylinders. One of the engines is Perkins 1104D-44TA, mechanically controlled and equipped with a feeding system with distributor injection pump. The second one is the Perkins 1104D-E44TA, electronically controlled, where fuel is supplied into the cylinders by means of the Common Rail system. During the tests, the engines operated according to two load characteristics. Hourly and specific fuel consumption as well as concentration levels of main components of exhaust fumes and smokiness have been iden-tified and compared.