The significant problem of evaluation of effective properties of Diesel engines, including, among others, ecological properties, is adoption of conditions of engine operation corresponding to conditions of use in testing procedures. The paper presents examples of stationary tests simulating the American dynamic test, i.e. Heavy Duty–Diesel–Transient– Test (HD–D–T–T). An engine with self-ignition and direct injection was tested during dynamic tests, i.e. HD–D–T–T and during stationary tests simulating HD–D–T–T. Results of the tests were analysed. The authors found high sensitivity of results of ecological tests on engine properties to conditions of tests as well as criteria of similarity of engine test conditions to conditions of operation of the engines. It was found that in relation to Diesel engines with other than vehicle applications, i.e. which are less commonly used than in automotive industry, it is necessary to prepare statistics of the results of research test synthesis.