In the present work, the influence of the inlet charge temperature is studied on the second law balance under the various operating engine speeds in DI Diesel engine. To this aim, the first law analysis is done by using the results of a three dimensional CFD model. The results show a good agreement with the experimental data. Also for the second law analysis, a developed in house computational code is applied. Behaviors of the results have a good accordance with the literature. The results show that an increase in the inlet charge temperature causes the indicated work availability, combustion irreversibility and entropy generation per cycle be reduced and the heat loss availability and exhaust gas availability be increased. Also the results reveal that the decrease in the combustion irreversibility and indicated work availability are more than the increase in the heat loss availability and exhaust gas availability when the inlet charge temperature is raised. (C) 2010 Elsevier Ltd. All rights reserved.