Shane van Gisbergen remains perfect through the first five races of the Supercars Championship, winning both 36-lap sprints at Sandown.
After breaking series history on Saturday, coming from 17th to finish first in a superb drive, the Kiwi turned two pole positions into two race wins on a wet track, proving he is the rain master.
The win equals a 25-year record, set by Mark Skaife, who won the opening five races of the 1994 season.
In the day's first race, the Aucklander lost the lead to teammate Jamie Whincup in the run to turn one on a wet circuit.
Walkinshaw-Andretti's Chaz Mostert tried to slip past the Red Bull pair and forced Whincup wide to take the lead at turn three, followed by van Gisbergen and Whincup.
Van Gisbergen took the lead on lap nine, after a safety car restart, and never looked back, maintaining and extending his lead, after mandatory pit stops.
Whincup came home second, ahead of Cam Waters, with Mostert slipping to fourth.
The second race saw a start-to-finish performance from the 2016 series champion, who thrived in the heavy Melbourne rain.
Rookie Jake Kostecki drove superbly to jump from seventh to second and secure his first podium, with David Reynolds third.