The upper limit for e ciency of a heat engine is thermal e ciency of a reversible Carnotrncycle, also called Carnot e ciency, C. Since a heat engine working at Carnot e ciencyrndelivers zero power with in nite time, the notion of extracting maximum possible powerrnoutput per cycle has been introduced. As a consequence the upper limit for e ciencyrnat maximum power of a heat engine, called Curzon-Ahlborn e ciency, CA, is de ned.rnDue to the need of providing a sustainable supply of energy and to strong concerns aboutrnthe environmental impact of the combustion of fossil fuels, performance e ciency of arnheat engine remains a major problem in thermodynamics. In this work we study thernperformance analyis of a heat engine where real gas is used as a working substance ofrnthe heat engine. The performance analysis is conducted through studying the cyclicrnthermodynamic process in the working substance of an endoreversible heat engine.rnWe perform a classical molecular dynamics simulation study of a heat engine operatingrnbetween two heat reservoirs and performing a Carnot-like cycle in a nite time over arnwide range of process rates. The heat engine is modeled to use real gas as the workingrnsubstance where we have used Lennard-Jones potential to consider the intermolecularrninteraction in the working gas. The piston speed and temperature ratio of cold and hotrnheat reservoirs are used as control parameters whereas e ciency and power output perrncycle are variable quantities of the engine. The variation of these dependent variables asrna function of the independent parameters is studied for two cases; when the piston movesrnwith uniform speed throughout the cycle and when it moves with constant but unequalrnspeed on the four branches of the cycle. It is shown that the e ciency of the Carnot-likernengine increases for a slower process rate but at the cost of power output. We also computernmaximum e ciency and e ciency at maximum power of the engine model considered andrnthe obtained result is in a good agreement with Carnot e ciency and Curzon-Ahlbornrne ciency respectively for the later case. It is also shown that the e ciency of the enginernxrnhighly increases when the cycle involves instant adiabatic process. Finally we determinernoptimum values for e ciency and power output per cycle and the corresponding processrnrate at which these values are attained where we use uni ed optimization criterion (rnrncriterion) to optimize between e ciency and power