The visitors were three nil up until the last ten minutes at Mansoura Stadium, thanks to a brace from Sayed Hamdi and a goal by Eric Bekoe.
However, Mansoura made a late recovery with quick fire goals from Mohamed Abou-Mahdi and Mohamed Al-Morsi, but that was not enough.
Petrojet took the lead in the 24th minute through Hamdi, who connected with Osama Mohamed's inch-perfect cross to head in past Mahmoud Abdoul-Saud.
Eleven minutes after the break, Hamdi, who scored a goal and set up another in the last 16 round 2-1 victory over Gaish, dished out a fine assist to new signing Bekoe.
The Ghanaian capped his full debut with a close-range strike from a tight angle, but keeper Aboul-Saud should have done better.
In the 63rd minute, Bekoe returned the favor to Hamdi, laying off a deft back heel to the relentless playmaker, who placed a wonderful shot into the top corner.
The game was virtually over but Mansoura skipper Abou-Mahdi scrambled in a point-blank finish to pull one back for the home side in the 80th minute.
Four minutes from time, the competition's top scorer Al-Morsi scored from the spot to take his tally to four goals and give Mansoura more hope of making a dramatic comeback.
But three injury-time minutes were not enough for the outsiders to get back into the game.