Dumbrell’s difficult weekend continued this morning when he managed just 21st on the grid following a driveline failure in qualifying.
From pole, Hazelwood was slow away from the line with wheelspin.
That let rookie Will Brown take the lead into Turn 1, where Shae Davies drove around the outside of Hazelwood to take second place.
A clearly cautious Hazelwood then let Jack Le Brocq through to third on the second lap, and fell back towards the group of Macauley Jones, Bryce Fullwood and Richard Muscat.
The Bigmate Racing driver picked his pace back up to establish a comfortable margin and started the final lap in third place, which would have been more than enough to win the title with Dumbrell down the order.
That became first, though, after MW Motorsport team-mates Davies and Le Brocq clashed at Turn 2 while fighting for the lead.
Le Brocq looked to have made a strong move around the outside, but Davies tagged and spun the Nissan on corner exit, the GoGetta Altima making heavy contact with the wall.
Davies crossed the line first, but was quickly handed a 25-second time penalty that dropped him to 11th and gave Hazelwood a sixth victory of the season and the round win.