It was the co-drivers' first time in the V8 Supercars at Sandown and young gun Cameron Waters led the way in the first 30-minute practice session.
Paired with Chaz Mostert for the Pirtek Enduro Cup, Waters, 21, has been the form driver in the Dunlop Series and is expected to be one of the quickest supporting drivers over the three long distance events.
In the Pepsi Max Crew Ford Falcon FG X, Waters recorded a 1min09.9067 lap, which was 0.2103sec quicker than second fastest Chris Pither, who shares the #34 Volvo with David Wall.
While main driver Mostert said during the session the car needed improvement, Waters seemed happy with the Falcon after he was just 0.38sec off Jamie Whincup's time in the first practice session.
"It's awesome to be quickest in the co-driver session," Waters said.
"Chaz rolled out this morning, car's pretty good... but Sunday's the day you've got to go quickest.
"Everything's going really well we're winning races and everyone's excited to be here. Hopefully we can press on and do that this weekend as well."
Mark Winterbottom's co-driver Steve Owen was home third, ahead of Paul Dumbrell (with Whincup) and Jonathon Webb (with Shane van Gisbergen).
DJR Team Penske's Marcos Ambrose finished the run 10th, while the other returning champ, Russell Ingall was 21st.
"All good," Ingall reported.
"Just blending in, no real problems - I haven't been sacked yet."