What is the most fuel efficient Turbojet engine by pass ratio of A380?

[UniverseAlien]

With four Rolls-Royce Turbojet engines attached on A380, I wonder, if the optimization of fuel efficiency as its prime design factor/variable? If so, may I know, what it is air by pass ratio?

 

[etudiant]

The A 380 engines have a bypass ratio of about 9.
While fuel economy is an important design factor, it is always a compromise with manufacturing cost and reliability equally important. Engines currently go for 5 years between overhauls or more. Maintaining stable performance throughout is a critical requirement.

 

[UniverseAlien]

Huh. . . I raise my thumb up! It comes to near perfect answer. Thank you very much.