كتب : وكالات
Both Cairo giants now have 49 points on top of the league table, with Zamalek leading on goal difference.
There are still six matches remaining in the domestic season.
Ahli broke the deadlock in Cairo after 15 minutes from an Ahmed Fathi powerful free-kick.
Petrojet, who played their first game with new manager Mohamed Omar, could have equalized before the break through Marawan Mohsen's header but Ahmed Adel parried the ball away.
Sayed Moawad doubled the lead seven minutes into the second-half with a rare long-range shot after a give and go with Ahmed Hassan.
Egypt captain Hassan was dismissed on the hour mark after receiving his second yellow card.