Nissan's Rick Kelly beat Craig Lowndes to top spot in opening practice for the Vodafone Gold Coast 600.
Kelly turned a 1:11.3245s in his Castrol Altima, shading Bathurst winner Lowndes by 0.1107 seconds.
Supercars title contenders Scott McLaughlin and Shane van Gisbergen were sixth and seventh, in a session curtailed by a crash for James Golding.
The final leg of the PIRTEK Enduro Cup got underway with the first of Friday's three, 30-minute practice sessions in warm and sunny conditions.
Jamie Whincup set the pace through the early stages, as drivers settled into the weekend's running, initially with a mix of full-timers and co-drivers.
Van Gisbergen displaced him with a 1:11.7767s nearing the halfway mark, when Whincup, McLaughlin and James Courtney were all within 0.06s.
Times were still coming down, David Reynolds, McLaughlin and Scott Pye moving to the top over the next phase, Pye with a 1:11.4412s.
Kelly edged ahead of Pye with five minutes to go, his 1:11.3245s standing into the final minute.
The session was then red-flagged, after Golding crashed his Garry Rogers Motorsport Commodore at the beach chicane.
That left Kelly on top in the Nissan he'll share with Garry Jacobson.
"We had a bit of a quicker car there, but McLaughlin's team-mate was, I don't know, warming up whatever and got in the way in the way a little bit in that last sector," Kelly said.
"It cost us a little bit. But it's challenging out there. You can see the damage on [Golding's] GRM car.
"Everyone is scraping walls to do the time, and this is what this place is about. I guess that's why the drivers enjoy it so much.
"There are some improvements to come from the car, but there are still, I think, from everyone in pitlane improvements to come from the drivers."
Lowndes – who leads the Enduro Cup points with Steven Richards – overshot Turn 12 in the final 10 minutes, but then improved to second before the session came to an end.
Pye handed over to co-driver Warren Luff for the closing stages, the Mobil 1 Boost Mobile Racing Commodore winding up third, ahead of Nick Percat and Whincup.
McLaughlin and van Gisbergen's earlier efforts were still good enough for sixth and seventh, Alex Premat finishing the session in the #17 Shell Ford.
Reynolds, rookie Jack Le Brocq and Nissan's Michael Caruso rounded out the top 10.
The best of the Tickford entries was the Chaz Mostert/James Moffat Falcon in 14th, ahead of team-mate Mark Winterbottom, Lee Holdsworth and Golding.
"[With] the concrete walls around here there's not much room for error," GRM director Barry Rogers said.
"The boys will get hard at it and we'll see what goes from there. [The team] will get straight into it. Head down, bum up, and away we go."
Practice 2, for co-drivers, starts at 1:45pm AEST on the Gold Coast.