It has been shown that the concept of exergue can be used in the analysis of ther-mo-dynamic efficiency. The concept incorporates both principles of thermodynamics. The factor of exergue efficiency is shown. The developed technique of defining the values of exergue losses occurring at the utilization of heat of internal combustion engine ex-haust gases is based. The technique is based on the entropy method. The obtained de-pendences determining the influence of various factors have been presented as well.