my car does 21.3mpg whatever I do or however I drive, (drive 11miles one way mainly dual carriageways) and still get the same mpg, it makes like a urrrrk/whump noise sometimes as the engine turns off, not all the time though, didn't know if this was connected? no irregular revs and also had the EGC or whatever it is and all fine (56 plate 2.0T FSI Quattro)