Strong winds at Symmons Plains made way for challenges aplenty as Shane van Gisbergen continued to chase history in the SuperSprint.
Monster Energy racer Cameron Waters found his stride early in the day, finishing both practice races with the fastest times of 50.8468 and 50.7244 seconds respectively.
But in the final qualifier, van Gisbergen lit up the track and asserted dominance, posting a record-setting 50.4923-second lap time.
The time eclipses that of Craig Lowndes, set in 2018.
"Job's not done yet" van Gisbergen said after landing pole, with a hungry Waters following just over .3 seconds later with Mostert just behind him.
Van Gisbergen's Red Bull Ampol teammate Jamie Whincup, who holds the most wins at Symmons (12), landed the fourth spot.
ELSEWHERE IN SPORT:
Waters got off to a statement start, taking the lead from van Gisbergen who was a tad tardy on the clutch.
Van Gisbergen followed closely behind, with Whincup keeping pace.
"It's not an excuse, but I was just looking around - I parked in the wrong spot - I wasn't parked back far enough to see the lights ... I muffed it anyway," van Gisbergen said.
"Cam was smart, [he] just brake-checked me at one to let Jamie go around the outside - it was a pretty good move.
"Once we got going, my car was awesome, braking was the biggest strength and that's what it has been all day.
"A few things we can work on for tomorrow but that was really good today."
Cam was smart, [he] just brake-checked me at one to let Jamie go around the outside - it was a pretty good move.Shane van Gisbergen on Cam Waters' opening move
Nick Percat's issue-ridden day continued into the race; the 32-year-old made contact at the hairpin on the opening lap, which sent him to the pits with a broken steering arm.
It was relatively clean racing aside from that, except for a close-call at the pit stop exit between Shell teammates Anton De Pasquale and Will Davison.
In lap nine, Waters gave van Gisbergen more than enough space to take the lead at turn six.
Mostert made his move soon after, pushing behind Whincup's tail as the latter overtook Waters, forcing the Monster Energy driver back two spots.
Waters continued to slide down, as De Pasquale used a slower Mostert pit stop to take third.
But van Gisbergen's fine form saw him to a race six victory, four seconds in front of Whincup and beating De Pasquale by an outstanding 9.7 seconds.
"Both cars were fast [and] for SVG to win the first six - that's pretty impressive considering just how close the cars are now," Whincup said.
"It's never been as even as it has been running, we've been running this car since 2013 ... so it just keeps getting closer and more competitive.
"To win the first six in this car has been really impressive."
The race win puts van Gisbergen among Allan Moffat and Mark Straife for winning the first six races of the season.
The Supercars action will return to Symmons Plains on Sunday from 10.45am.