Michael Caruso topped the morning session at the all-in official Supercars pre-season test at Sydney Motorsport Park.
The Nissan driver, debuting a brand new chassis, jumped to the classy end of the timing screen an hour into the 3.5-hour morning session with a 1m29.470s to go second behind early leader and teammate Rick Kelly.
He then banked a 1m29.179s to knock Kelly off top spot, that time remaining unbeaten at the lunch break.
Kelly's 1m29.213s, set inside the first hour, was good enough for second at the break.
DJR Team Penske's Fabian Coulthard was the best of 'big two' teams from 2017, sitting third with a 1m29.620s set during the second hour of the session.
He was very closely followed by Erebus star David Reynolds, who was the best of the brand new ZB Commodores. He handed his car over to fellow Bathurst 1000 winner Luke Youlden late in the session after setting his 1m29.627s.
Scott Pye gave the re-structured Walkinshaw Andretti United squad a decent first hit-out with the fifth best time of the session, while Craig Lowndes was the best of the Triple Eight cars with a 1m29.687s. The veteran was actually the only regular T8 driver to crack the Top 10, with Shane van Gisbergen 19th and Jamie Whincup dead last.
There are also reports on the official Supercars site that van Gisbergen and former Tekno boss/co-driver Jono Webb came to blows both on and off the track during the session, minor contact on the front straight leading to a heated confrontation in the garage afterwards.
Rookie Jack Le Brocq was seventh quickest in the same T8-built, Tekno-run Commodore that Webb had been driving when he allegedly bumped doors with van Gisbergen.
WAU's James Courtney, Erebus rookie Anton de Pasquale, and 23Red's Will Davison rounded out the Top 10.
There wasn't a single Tickford Ford in that Top 10, Cam Waters the best in 12th while Mark Winterbottom was 17th, Chaz Mostert 23rd, and newcomer Richie Stanaway 25th.
Tickford's new enduro signing James Moffat also got some laps in Mostert's Falcon, with the pair expected to team up for the long-distance races later in the year.
Scott McLaughlin was 15th quickest in his Penske Ford.