Pep Guardiola's men extended their English top-flight record of 16 consecutive wins by easing past Tottenham Hotspur 3-0, while Manchester United and Liverpool stumbled once more.
Leicester moved level on points with United in second by inflicting Liverpool's third consecutive defeat with a three-goal blitz in six minutes to win 3-1 at the King Power stadium.
United's form is not much better with just one win in their last five to let hopes of a first league title in eight years slip away.
City were floundering in the bottom half of the table when they last suffered defeat, 23 games ago against Tottenham. In the three months since, the league leaders have picked up 41 points to Spurs' 16.
That stat illustrates the consistency City have found in a season when all the other contenders have had their struggles.
After a run of just two wins in 10 games, Liverpool are languishing in sixth place -- two points adrift of the top four -- following wins for Chelsea and West Ham on Monday.
Even if City's standards do slip in the coming months as they turn their attention towards trying to win a first ever Champions League, there is no indication any of the chasing pack are capable of putting the run together needed to put them under any pressure.
"We won't let them run away with it -- we're playing them soon. We're not giving it away early," insisted United boss Ole Gunnar Solskjaer.
But only last weekend he conceded his side are not title contenders and it showed as they were held 1-1 on Sunday by a West Brom side that had conceded 24 goals in their previous six home games.
Ederson shines as Alisson stumbles
The story of City and Liverpool's contrasting fortunes is summed up in the form of their goalkeepers at the moment.
Brazilian internationals Alisson Becker and Ederson are used to glowing reviews for their exploits since arriving in England.
Alisson had cemented his place as Brazil's first choice stopper thanks to his role in Liverpool's success over the previous two seasons, but that spot might be in jeopardy after his latest disastrous error provided a stark contrast to Ederson's continued excellence.
Having already made two costly howlers in Liverpool's 4-1 thrashing against City last weekend, Alisson was at it again with a calamitous error to turn Saturday's clash in Leicester's favour.
With the game level at 1-1, Alisson needlessly rushed off his line, collided with Liverpool debutant Ozan Kabak and miscued his clearance to Jamie Vardy, who slotted into the empty net.
Just hours later the flawless Ederson rubbed salt into his wounds by keeping his 14th clean sheet in his last 16 games and providing a superb assist for Ilkay Gundogan.
Ederson's long pass was perfectly placed for Gundogan to score his second and City's third of the game and the accuracy prompted Pep Guardiola to suggest his keeper could yet become City's penalty taker.
Southampton on the slide
The high of beating champions Liverpool in January must seem like a distant memory for Southampton, who have slumped so badly that Sunday's 2-1 loss against Wolves made unwanted history for Ralph Hasenhuttl's team.
After beating Jurgen Klopp's side and knocking Arsenal out of the FA Cup, Southampton were hailed as a team on the rise with European qualification on the agenda.
Instead, they have lost a club record six successive league games since then and sit well adrift of any continental aspirations in 13th place.
A 9-0 humiliation at Manchester United seems to have shattered Southampton's morale and there is no revival in sight after their latest defeat against Wolves.
Standout matches today