A method for forming plastic preforms into plastic bottles has a first and a second operating mode, wherein the respective operating modes being selectively chosen by an operator as required. In in the first operating mode, i.e. a quality mode, a connection is established between a valve block and a pressure reservoir of the second pressure level in only one direction, from a valve block towards the pressure reservoir, i.e. a compressed air recycling mode, and in a second operating mode, i.e. an efficiency approach, a connection is established between the valve block and the pressure reservoir of the second pressure level in both directions, i.e. from the valve block towards the pressure reservoir and from the pressure reservoir towards the valve block.