Total consumption of all types of energies is rather high nowadays with constant tendency of increasing. Transport section is one of the highest consumers of energy obtained from fossil fuels. It is absolutely clear that the reduction of energy consumption and the protection of environment - exhaust emission reduction, i. e. cleaner air, will be one of the main tasks of automotive industry in the first decades of the 21st century. In spite of its superiority over the petrol engine in respect of the fuel consumption, a diesel engine "suffers" from the increased exhaust emission, particles and NOx first of all and also from the noise and vibrations. The paper gives a review of fuel efficiency of conventional design tractors diesel engines in relation to new design. .