To give some perspective, the hourly fuel consumption for Concorde is almost identical at Mach 2 than at max subsonic speed... And Concorde powerplant had at s

To give some perspective, the hourly fuel consumption for Concorde is almost identical at Mach 2 than at max subsonic speed... And Concorde powerplant had at some point the highest overall thermal efficiency at max speed: https://en.wikipedia.org/wiki/Rolls-Royce/Snecma_Olympus_593 https://en.wikipedia.org/wiki/Rolls-Royce/Snecma_Olympus_593 The overall thermal efficiency of the engine in supersonic cruising flight (supercruise) was about 43%, which at the time was the highest figure recorded for any normal thermodynamic machine.