A grass mowing machine comprise a plurality of cutting units an internal combustion engine that runs at a normal engine speed or at an economy mode speed slower than normal engine speed, the engine driving hydraulic pumps connected to a circuit having a plurality of sub-circuits including a mower sub-circuit 158 and a raise/lower sub-circuit and a diverter valve 172 diverting hydraulic flow from the raise/lower sub-circuit to the mowing sub-circuit 130 when the engine runs at the reduced or economy mode speed and the cutting units are at the lowered position. Also disclosed is a mowing machine having an electronic control unit actuating a diverter valve.
