City are runaway leaders in the new league table, with four wins and 17 goals in all competitions.
But perfectionist Guardiola wants more from his millionaire superstars.
He said: “To take it to the next level we have to improve a lot to things.
“Now, after four games in the Premier League, I would like to tell our fans that the way we have played up until now, it will not one good enough to win the title.
“So we have to improve to win the Premier League.
“Of course, we are so happy with the results and the way we are playing after two months.
“But it is not enough to win the Premier League or the bigger target of the Champions League. We have to improve.
“But it's normal. All the teams have to improve, especially for the managers who are new - like United, like us, like Chelsea."