The present invention relates to a self-propelled agricultural machine, comprising: elements (5) for gathering and/or processing crops; an engine (1) operable to travel the machine through a first driving mechanism (3) and to drive the operation of said elements through a second driving mechanism (4); and a control unit (6) for controlling engine RPM, characterized in that the control unit (6) is configured for controlling the engine RPM (ni) on the basis of a target RPM (ns), which is in turn based on an assessment of the imposed engine load (Ti), wherein in at least in one sub-range between 0% and 100% of the maximum load, the target RPM is a constantly rising function of said engine load. The present invention relates also to a method of controlling the RPM of the engine.