Kostecki was largely untroubled within the closing 20-lapper of the weekend with a problem from Cam Waters persistent however at no level overly harmful.
Even higher for Kostecki was that his key title rivals all failed to fireside, Shane van Gisbergen the very best of them in fifth place.
That provides Kostecki a 137-point lead over van Gisbergen, whereas Broc Feeney is now 258 factors again after ending final in that race.
That was because of being hip-and-shouldered off the highway on the final nook on the penultimate lap by David Reynolds as they fought over ninth place.
Will Brown, in the meantime, is a hefty 258 factors again after a tough day that ended with a Thirteenth-place end.
Kostecki made a strong begin to the race from pole place, his largest problem coming from Nick Percat who vaulted off the second row and had a glance across the outdoors into Flip 1.
Percat ultimately needed to accept second, whereas Waters dropped from second to fourth, earlier than working his well beyond Thomas Randle and again into third on the primary lap.
Thomas Randle, Tickford Racing Ford Mustang GT
Picture by: Edge Photographics
Third then turned second on the subsequent lap when he marched previous Percat on the run into Flip 1.
By that time Kostecki was a second down the highway, the pair see-sawing round that margin throughout a lot of the first stint.
It wasn’t till the stops neared that Kostecki was capable of pull additional clear, the hole out to greater than two seconds when Waters stopped.
Kostecki lined Waters off the subsequent time round, resuming together with his two-second lead intact.
From there it was a easy case of managing the hole, Kostecki cruising to the road as he scored a clear sweep by nine-tenths of a second.
“Superior effort by everybody at Erebus,” mentioned Kostecki. “It was unbelievable execution the entire weekend, unbelievable pitstops. All the effort that is gone into this 12 months is beginning to repay.
“The automobile has been lightning fast all weekend. I needed to maintain off Cam there, he was respiratory down my neck and pushing me the entire race. I am glad to remove the clear sweep. First one for myself and first one for the crew.”
Randle capped off a career-best weekend with third place, whereas Percat scored his finest results of the season to this point in fourth.
The season continues with the primary of two endurance races, the Sandown 500 on September 15-17.