Mark Winterbottom has set the pace on a drying track in Practice 1 for the OTR SuperSprint at The Bend Motorsport Park.

The Team 18 driver guided the #18 Irwin Tools ZB Commodore to a 1:50.4944s with the chequered flag out on the half-hour opening session for the Repco Supercars Championship field.

Shane van Gisbergen similarly improved late on, but the championship leader fell just shy of Winterbottom in clocking a 1:50.5335s in the #97 Red Bull Ampol ZB Commodore.

The most recent race winner, Chaz Mostert, ended up third in his #25 Mobil 1 Appliances Online ZB Commodore, ahead of James Courtney (#44 Boost Mobile Mustang) and Anton De Pasquale (#11 Shell V-Power Mustang).

The session began on a track left slippery from a shower earlier in the morning, and most of the field headed out on wet tyres.

Jamie Whincup (#88 Red Bull Ampol ZB Commodore) kicked things off with a 2:04.9006s, then a 2:03.0825s.

As he pitted, Tim Slade (#3 CoolDrive Mustang) moved the marker to a 2:03.0816s before Will Davison (#17 Shell V-Power Mustang), who was among the first to switch from wets to slicks, clocked a 2:02.1652s.

Davison backed that up with a 2:00.8306s next time around and, from there, all the pace was on slick tyres.

Mostert went to a 2:00.5540s just past the halfway mark, Davison responded with a 1:59.1434s, and Mostert grabbed top spot back with a 1:59.0734s.

The Walkinshaw Andretti United driver continued to make time, setting a 1:57.5342s and a 1:56.4291s on consecutive laps, before the fastest time was reset four times in the 23rd minute.

Nick Percat (#8 R&J Batteries ZB Commodore) clocked a 1:56.2935s, then van Gisbergen a 1:56.0766s, Andre Heimgartner (#7 Ned Mustang) a 1:56.0133s, and Whincup a 1:55.4387s.

Whincup and Percat were both threatening to go faster again when a red flag came in the 24th minute due to Courtney spinning at Turn 6 and beaching the #44 Tickford Racing entry.

With an obvious dry line having formed, the pace continued to step up when the field was unleashed onto the circuit again.

Davison was back on top with a 1:53.3645s but that stood for moments before van Gisbergen went to a 1:52.6990s.

Heimgartner then set a 1:52.2556s, Whincup a 1:51.5096s, and Mostert a 1:51.4412s despite a slide through the final corner.

Just before the chequered flag, van Gisbergen came through with a 1:51.3037s, Scott Pye (#20 DeWalt ZB Commodore) a 1:51.1124s, and Courtney subsequently a 1:50.9252s.

The last to advance the benchmark was Winterbottom, while van Gisbergen had been shuffled all the way back to eighth before he completed his final lap.

The Triple Eight Race Engineering driver bumped Mostert, who had just achieved a 1:50.6025s, back to third, ahead of Courtney, De Pasquale, Cameron Waters (#6 Monster Energy Mustang), Davison, Will Brown (#9 Ozland Group Solutions ZB Commodore), Pye, and Slade.

A second covered the top 12, which was rounded out by Percat and Jack Le Brocq (#5 Truck Assist Mustang), while Whincup ended up 13th at 1.0152s off the pace on a 1:51.5096s.

For reference, a low- to mid-’48’ was the best pace in light rain during practice last year on the International Circuit.

Thomas Randle (#55 Castrol Mustang) was best of the two wildcards in 15th, with Kurt Kostecki (#27 Mobil 1 ZB Commodore) 24th in the 26-car field.

Practice 2, another 30-minute session, starts at 10:45 local time/11:15 AEST.

Results: Practice 1