What causes inefficiency in diesel or Otto engine? the publications do not explain and University professors could not explain realistically, so engines are as inefficient as were in XIX century, because nobody knows how to remove the inefficiency causes. I expect the those hide in poor design and blame wrong trend of research for inability to find flaws of design. Modern engine does not exists as all those are invented in XIX century and are very inefficient, so claiming "Highly efficient or modern diesel engine is misleading and dishonest. The current trend of research resulted in improving rethorics, but engines. I suggest leaving rethorics to English teachers and end dishonest misleading. The efficiency below 50 % is a huge inefficiency and nobody knows what causes that in combustion engines. Without finding the causes one cannot improve engines.