The visitors from the Coca-Cola Championship did their best, but City were just so much better it was almost embarrassing to watch at the end.
Stephen Ireland staked his claim for a regular place in Mark Hughes' side with a glittering performance and City's early goal.
Scunthorpe hit back with a Jonathan Forte equaliser and never gave up. But once Roque Santa Cruz headed his first goal for City to restore their lead before the break, there was only going to be one winner.
The second period saw Carlos Tevez outstanding. He scored one and tormented Scunthorpe relentlessly.
Michael Johnson and Joleon Lescott added further goals, and it could easily have been more with substitute Vladimir Weiss missing a late hat-trick as City threatened to run riot.