With Chelsea being held to a 1-1 draw by Brighton earlier on Wednesday and Liverpool losing 1-0 to Leicester the day before, City capitalised by seeing off a spirited Bees side.
Phil Foden settled the encounter with his fifth league goal of the season early in the first half, superbly finishing first time from Kevin de Bruyne's whipped ball.
The win was City's 10th in a row and leaves them in a commanding position at the top. The previous two occasions City rounded off December in first place in the Premier League - in 2011-12 and 2017-18 - they went on to win the title.
"There are 54 points to play for," Guardiola said.
"All of you, thank you for your nice words because we win but I am not going to believe any words you say about it is already done or expected because Chelsea and Liverpool are more than exceptional. One is champions of Europe and the other has been our big rivals over the years.
"The distance is not because they drop points but because we win 10 games in a row."
City were looking to equal the club's top-flight record of scoring at least four goals in four successive games set in 1905 but they rarely carved open a hard-working Bees side.
Ivan Toney was fortunate to go unpunished for catching Fernandinho with his studs as the City midfielder lay on the ground shortly before half-time.
The visitors went close to doubling their lead soon after the break when De Bruyne and Foden again linked up, with the latter heading his team-mate's cross just wide of the post.
De Bruyne struck the base of the upright with a fierce low drive from distance, while Dias had a header ruled out for a marginal offside, but in the end Foden's first-half strike was enough to seal the win.
Brentford, meanwhile, remain 14th with 20 points - nine clear of the relegation zone as they look to ensure a second season in the top flight.
Indeed, the decisive strike had come just moments after the hosts came close to scoring themselves but Ederson reacted well to keep out a cross that bounced towards the City goal off Ruben Dias, before Yoane Wissa's deflected strike was cleared off the line.