The Reds ended their 30-year wait for a title last week when City were beaten by Chelsea, but City put a dampener of their celebrations with an emphatic victory at the Etihad.
The visitors almost broke the deadlock when Mohamed Salah's low drive rocketed off the post, and it proved to be a costly miss.
From then on City took full control of a first-half which saw them score three goals in 20 minutes, first through Kevin De Bruyne, who converted from the penalty spot after Joe Gomez fouled Raheem Sterling.
Former Liverpool man Sterling then got the second after finishing off an outstanding counter-attack.
Phil Foden played a sharp one-two with De Bruyne before finishing cooly with his opposite foot past an onrushing Alisson.
A second-half own-goal from Alex Oxlade-Chamberlain rounded off a result which reminded the league that next season will be a fresh start.
And speaking after the game, Sterling told Sky Sports that City were already thinking about how to reclaim their title.
He said: "They (Liverpool) have been brilliant all year, we wanted to have a good game against them.
"We knew we were behind, have been disappointing at times. We had a test against the current champions to make a point and we did brilliant. Next season started today and we did well.
"This is a team that is evolving and changing, You can see the maturity Phil (Foden) is playing with. I think in the future we have some great players."