A method of forming plastic preforms into plastic bottles comprising the steps: - placing a plastic preform to be expanded in a blow mould, wherein said blow mould comprising at least two side parts and a bottom part; - inserting a stretching rod through the mouth of the plastic preform into the interior of the plastic preform to stretch it in its longitudinal direction; - applying a first pressure level to the plastic preform; - applying the plastic preform with at least one second pressure level (P+, Pi), wherein the second pressure level (P+, Pi) differs from the first pressure level and is preferably higher than the first pressure level; - applying the plastic preform with a third pressure level, wherein this third pressure level differing from the second pressure level (P+) and preferably being higher than the second pressure level (P+); wherein a pressure reservoir is assigned to each pressure level, wherein the method comprises a first and a second mode of operation, wherein the respective modes of operation being selectively chosen by an operator as required, characterised in that in the first operating mode, i.e. in a quality operation, a connection is established between a valve block and a pressure reservoir of the second pressure level (P+, Pi) in only one direction, from a valve block towards the pressure reservoir, i.e. a compressed air recycling, 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 (P+, Pi) in both directions, i.e. from the valve block towards the pressure reservoir and from the pressure reservoir towards the valve block. - placing a plastic preform to be expanded in a blow mould, wherein said blow mould comprising at least two side parts and a bottom part; - inserting a stretching rod through the mouth of the plastic preform into the interior of the plastic preform to stretch it in its longitudinal direction; - applying a first pressure level to the plastic preform; - applying the plastic preform with at least one second pressure level (P+, Pi), wherein the second pressure level (P+, Pi) differs from the first pressure level and is preferably higher than the first pressure level; - applying the plastic preform with a third pressure level, wherein this third pressure level differing from the second pressure level (P+) and preferably being higher than the second pressure level (P+); wherein a pressure reservoir is assigned to each pressure level, wherein the method comprises a first and a second mode of operation, wherein the respective modes of operation being selectively chosen by an operator as required, characterised in that in the first operating mode, i.e. in a quality operation, a connection is established between a valve block and a pressure reservoir of the second pressure level (P+, Pi) in only one direction, from a valve block towards the pressure reservoir, i.e. a compressed air recycling, 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 (P+, Pi) in both directions, i.e. from the valve block towards the pressure reservoir and from the pressure reservoir towards the valve block.