City were lacklustre in the first half but Alvaro Negredo's first goal on the stroke of half-time changed the course of the game.
Negredo's quickfire double either side of the interval took his total for the campaign to 21, two ahead of Sergio Aguero.
Aguero soon cut into that deficit, scoring within a minute of coming on to replace the Spaniard.
Edin Dzeko also maintained his recent form with his brace taking him to a not insignificant 15 for the season as City took their season's tally to 99.
Lack of intensity
The game lacked the intensity of recent Premier League games but chances were still created by both sides in what proved an evenly-contested first half.
Dzeko spurned a number of them, first heading over the bar in the second minute and then missing the target again moments later after combining with Negredo.
Blackburn were lacking their star striker Jordan Rhodes but the Championship side were determined to make a fight of it and in Tom Cairney, recently signed
on a permanent deal from Hull, they had one of the game's most influential midfielders.
DJ Campbell almost caught City's second-choice keeper Costel Pantilimon in possession and Cairney had their first attempt on goal when Joleon Lescott blocked his shot.
Ben Marshall also sent a shot into the stand before Cairney was felled on the edge of the area after a good run. Marshall could only pick out Pantilimon from the free-kick.
Javi Garcia went close for City with a fizzing shot from outside the area which former England No 1 Paul Robinson parried but Dzeko was again wasteful, shooting over twice more.
Much as they did when the sides met at Ewood Park earlier this month, City grabbed the lead just before half-time through Negredo.
It came after a swift counter-attack by the hosts, with Fernandinho combining with Navas before clipping in a cross for Negredo to head home.
Any thoughts the game might continue to follow the same script as the last encounter were dispelled by City's start to the second half.
Negredo doubled the lead within two minutes of the restart as he raced onto a fine ball from newly-introduced substitute Aleksandar Kolarov to clip a fine shot over the advancing Simon Eastwood.
Eastwood's first task, having replaced Robinson at half-time, was to pick the ball out of the net.
Blackburn, to their credit, responded positively and the introduction of Josh King up front for Campbell made a difference.
He twice went close with a header over and a shot which was well saved by Pantilimon.
Jason Lowe was denied a corner after a shot was deflected narrowly wide off Lescott, and that appeared to be the prompt for City to step up the tempo.
Dzeko made it 3-0 after 67 minutes with a quick first-time finish after a good run and cut-back by Navas.
That as good as made the result safe and Manuel Pellegrini decided to send on Aguero for his comeback.
The Argentinian had been on the field just 50 seconds when the ball fell to him in the box and he lashed a shot past Eastwood after 73 minutes.
Six minutes later City were at it again as Dzeko swept home from another good Navas cross.
Milner thought he had clinched City's century when the closing moments when he sent a powerful free-kick curling wide of the far post.