The Black Cats had defended doggedly before a swift City counter attack ended with Aguero prodding in Raheem Sterling’s low cross from close range.
The visitors then clicked into gear as David Silva fed the explosive Leroy Sane for the Germany winger to double their lead after the break.
Jermain Defoe did find the net in a rare Sunderland attack late on, but his header was ruled out for offside.
The result could have been more comfortable for City, but Sunderland keeper Jordan Pickford saved well from Aguero.
For all City’s possession, it was the hosts who threatened first, Defoe hitting the post with a bouncing effort from outside the box that had Willy Caballero beaten.
Fabio Borini headed wide from the rebound, and any hopes David Moyes’ side had of taking three points seemed to evaporate with that miss.
City still fighting on three fronts
With Chelsea not in action until Monday, Manchester City took the chance to move within eight points of the runaway leaders with a confident performance at the Stadium of Light.
Pep Guardiola will hope this victory, and an earlier win for second-placed Tottenham, may see Antonio Conte’s side begin to feel the pressure.
It was a fourth league win on the trot for Guardiola’s outfit, who are building momentum and can continue to crank up the heat up on their title rivals when they face Stoke in a game in hand on Wednesday.
But they are fighting on three fronts, with this routine victory marking the start of five games in 15 days that include a Champions League last-16 second-leg trip to Monaco and a FA Cup quarter-final at Middlesbrough.
It is a problem Guardiola will welcome, but does the Spaniard’s squad have the depth to cope?
He made five changes to the side which thrashed Huddersfield 5-1 in midweek and could afford to drop Kevin de Bruyne for Silva, whose incisive passing helped unlock a resilient Sunderland.
Aguero proves his worth
So what about Aguero? The Argentine’s future was thrust into the spotlight after he lost his place to 19-year-old Gabriel Jesus last month, and he admitted this week his position at the club was unclear.
Guardiola can be ruthless when he feels a player does not fit into his system, just ask Joe Hart, but a metatarsal injury for Brazil forward Jesus appears to have offered Aguero a lifeline.
The 28-year-old has now scored five goals in his last three games in all competitions for City, having gone six games without finding the net before that.
Guardiola is building a team spearheaded by youth, and Aguero’s poacher-like presence was complemented once again by the creativity of Sterling and Sane.
Sterling’s trickery proved a constant threat down the right and Sane’s sheer speed gave City an outlet on the opposite flank, gliding beyond his marker to finish left-footed past Pickford for the visitors’ second.
No miracle cure for Moyes
Sunderland have become masters of beating the drop when appearing dead and buried in recent seasons, but they may have left the escape act too late this time around.
Sitting six points from safety at the bottom of the Premier League, the Black Cats’ fate lies out of their hands.
And with relegation rivals Crystal Palace, Swansea and Leicester enjoying a recent upturn in form, David Moyes needs something of a miracle if his side are to spring a late recovery.
Moyes’ side have taken points off Liverpool and Tottenham at home since the turn of the year, and did frustrate City for long spells in the first half, but once the visitors found a breakthrough they were able to keep Sunderland at arm’s length.
Man of the match – David Silva (Man City)