V8 Supercar Championship Series leader Jamie Whincup restored order at the Queensland House and Land.com 300 on Saturday with victory over Jim Beam Racing's James Courtney and Ford Performance Racing's Mark Winterbottom.

But he admitted it could have been a different story had his and the team's mentality not changed from the last event in Melbourne at the Norton 360 Sandown Challenge.

"Sandown was just a poor result from everybody across the board," Whincup explained. "We were thinking about next year [when we will defect to Holden] and getting way too far ahead of ourselves with everything that was going on."

Whincup was disappointed though with the way he extended his Championship lead over closest challengers Will Davison and Garth Tander, who both failed to finish today's race.

"That's not racing," Whincup said. "It's really unfortunate that my biggest rivals got knocked out today. We need to get out there racing and settle this thing on the track, that's how it should be."

Davison has dropped 267 points behind with the result: "After qualifying we sacrificed the race running on hard tyres and a mid-field result would have been tough enough, let alone a DNF," Davison said.

"At this stage of the Championship you really can't afford to do that, so a DNF is devastating. On a positive note, we have fresh soft tyres for tomorrow, not many others do, so we'll try claw back as many points back as we can."

Whincup would still not let up coming into the unpredictable endurance events of the L&H 500 at Phillip Island and the Supercheap Auto Bathurst 1000.

"You still keep racing (despite a lead) and pushing hard. That whole lead can turn into a deficit in one day at Bathurst."

Both TeamVodafone cars suffered oil leaks, the worst of which forcing Craig Lowndes to also retire. Whincup admitted it was a great concern with one race remaining tomorrow.

The day ended early for Lowndes off the line when he missed the start and then suffered massive oil loss problems. Lowndes' TeamVodafone car dumped a massive amount of oil on one corner, causing havoc for the field.

The worst casualty was the Orrcon Steel FPR Falcon of Winterbottom who at one moment was second and the next sliding off the track on the greasy oil. He ended up with oil all over his windscreen which forced an early pit stop.

Whincup almost joined him on the same lap but miraculously held on to a car that was almost sliding sideways. It was a mistake on lap eight that cost Whincup the lead to Courtney. He got his man back 10 laps later when he regained the lead having made up around three tenths of a second per lap.

Courtney continued the success of recent events as the Jim Beam team begin to show real Championship winning potential.

"We always had the right ingredients, it was just a matter of getting the amounts right," Courtney said.

Whincups' closest rival Davison lost plenty of ground in the Championship hunt with his failure to finish while third-placed Tander also had a bad day when his Toll HRT Commodore had problems with the wheel change in the pits.

Supercheap Auto Racing's rookie, Tim Slade earned his first V8 Supercar Championship Series top 10 finish in today's race for the Queensland House and Land.com 300 and set a new lap record in the process at 1m 10.8948s.

"I feel we've been improving every round, so to earn a top 10 finish is incredibly satisfying, let alone a new lap record," Slade said. "My Supercheap Auto Racing Commodore was good all race and with a great strategy call by Paul [Morris] we were able to switch to the soft tyres with about 10 laps to go. We were able to pass a few towards the end and come home with a great result."

The Queensland House and Land.com 300 continues tomorrow with the short sharp 20 minute qualifying session followed by the longer 200km race from 1pm.