In the current age, pollutant emissions reduction and fuel consumption is less an alternative or secondary option but rather some categorical imperative to be treated with all seriousness. We have to do so with a set of priorities. In addition to designing environmentally friendly engines, which will consume and pollute less if possible even at all, there have to be taken into account also the existing and running engines until this time, and the performance level, which hasn’t been designed taking into account the latest criteria in the field. In the present work it is discussed the problem of testing brand new engines and systems, and also of analyzing or, if one can say so, of investigating the existing systems, but with some significant improvements which have to satisfy the actual requirements of less pollution and low consumption. Reviewing and carefully studying the power of existing diesel engines in use today may lead to a series of constructive solutions and ways of optimizing the injection system so as the pollutant emissions and fuel consumption to be reduced, while engine power performance increases.