كتب : Omar AbdelAziz
The title holders now have 52 points on top of the table, while Mahalla remain 12th with 29.
Ahli are only one point ahead of second-placed Ismaili, who thrashed Arab Contractors in Ismailia.
The Red Devils, who missed influential duo Mohamed Barakat and Ahmed Hassan, seemed to be lacking venom against a resilient Mahalla team.
Manuel Jose started with Osama Hosni alongside Flavio Amado upfront, keeping Mohamed Abou-Treika on the bench.
A cagey start from both sides prompted little action inside the opening half-hour, which suggested that the defending champions won't have an easy ride.
Mahalla keeper Ibrahim Farag was called into action in the 31st minute when he blocked a Flavio tight-angled header.
Two minutes later, the home side responded when Nader Al-Ashri's effort went agonizingly wide of the left post, in what was the best chance of the first half.
Nine minutes from the break, Jose introduced Qatari forward Hussein Yasser at the expense of full-back Ahmed Sedik.
Abou-Treika came on for Hosni at half-time, as the latter has hardly touched the ball in the first half.
The second half witnessed no improvement in terms of chances at both ends, as league strugglers Mahalla seemed to be desperate for the point.
Ahmed Fathi tested Farag from 35 yards and the Mahalla guardian couldn't handle the bouncing ball, but there was no response from Ahli's strikers on the rebound.
Jose brought on Ahmed Belal for Sayed Moawad to shore up the frontline, but the Portuguese's attempts went in vain.
Moetaz Eno was close to snatching a dramatic winner in injury time when he fired a long-range shot that went inches wide.