Dean Smith made five changes from Villa’s last Premier League encounter – a 2-1 win at Burnley on New Year’s Day – as Norwegian keeper Orjan Nyland was handed his first league start and there was a debut for midfielder Danny Drinkwater, while Ahmed Elmohamady, Conor Hourihane and Anwar El Ghazi were recalled.
City boss Pep Guardiola made four changes from the team that started the 2-1 home win over Everton on January 1 as goalkeeper Ederson returned from suspension while John Stones came in, but Raheem Sterling was left on the bench.
City came into the game in good form with eight wins from nine in all competitions and they took control of proceedings early on at Villa Park.
A Villa defensive clearance from Aguero’s low cross was pounced on by Joao Cancelo and his effort swerved just wide of Nyland’s far corner of the goal on eight minutes, before Ezri Konsa produced a fine clearance to prevent Gabriel Jesus or Aguero getting on the end of a Mahrez cross.
However, the City pressure paid off when they took the lead on 18 minutes as Mahrez picked up the ball in the right channel and skipped his way past former Leicester team-mate Drinkwater before hammering a low strike inside Nyland’s post.
Drinkwater’s debut went from bad to worse on 24 minutes when he failed to clear the danger inside his own area and was robbed by Jesus as the ball fell to Mahrez to lash home his and City’s second.
It was virtually game over four minutes later as Aguero was allowed to advance towards goal by the Villa backline before hitting a 20-yard strike past Nyland.
City heaped more misery on Villa just before half-time when Kevin De Bruyne produced a superb cross from the right to pick out Jesus at the back post and the Brazilian tucked the ball away from a tight angle.
There was no let-up from City after the break as Aguero became the fifth highest scorer in Premier League history on 176 goals when he collected a David Silva pass inside the area and put a right-foot effort beyond Nyland and into the far corner of the net on 57 minutes.
Tyrone Mings denied City a sixth on 65 minutes when he hooked a Jesus effort off the line after good work by Silva down the left edge of the box.
City picked their way through the Villa defence again on 78 minutes but this time Nyland denied Jesus at his near post, before the Brazilian somehow fired over from close range following the resulting corner.
Aguero then overtook Alan Shearer’s previous record for Premier League hat-tricks in the 81st minute when Kortney Hause gifted the ball to Mahrez and he teed up the Argentine to smash in City’s sixth of the game for his 12th treble in England.
Villa grabbed a late consolation goal when El Ghazi scored from the penalty spot after Ilkay Gundogan fouled Trezeguet in the area.
City move two points above Leicester into second place and 14 points behind Liverpool, while Villa remain in the final relegation place a point behind a resurgent Watford.