A dominant display from City saw them go 4-0 up before the half-time whistle, before they added a further two goals in the second half.
Braces from Erling Haaland and Phil Foden all but sealed the three points for the hosts in the opening 45, before both went on to complete their hat-tricks after the interval.
Antony pulled one back for the Reds just before the hour mark, making it 4-1, and Anthony Martial scored twice on his return from injury, but these were nothing more than consolation goals as Erik ten Hag's side lost 6-3.
City were the dominant team from the off, and it would take just three minutes before they were threatening United's goal.