After winning yesterday's Trophy race before following up with a storming display in the second race, Johnson lead from start to finish, keeping it clean as those around him struggled with the wet track.
“I can tell you, in these conditions, being here for 25-odd years makes a big difference of where to go, and I could see what was happening behind me,” Johnson told Stan Sport. “[There was] a lot of water, a lot of standing water and they did the right thing calling that race early.”
A rolling start due to the wet weather saw pole-sitter Johnson challenged by Andrew Fisher, who started alongside him and went toe-to-toe with Johnson around Hell Corner before the Mustang marched away.
As the field climbed Mount Panorama, Johnson headed Fisher's Holden as Jamie Tilley made the most ground in his Mustang, climbing to third place from fifth to be all over the back of the Torana into Forrest's Elbow.
The opening-lap battle between the top three was paused as championship leader Adam Bressington put two wheels on the grass down Conrod, spinning his Camaro which appeared closed to rolling over before it ended up in the sand trap at The Chase.
With the Safety Car deployed to retrieve the stricken Chevrolet, Johnson headed the field with Fisher, Jamie Tilley, Jim Pollicina, Ryan Hansford and John Bowe. Bowe was pulled into the pits with his Torana's rain light malfunctioning, officials ruling him out of the race and elevating Cameron Tilley into sixth.
As the green flag was waved as the field completed its third lap, Johnson took control as Jamie Tilley looked up the inside of Fisher, who went straight on at Hell Corner to miraculously avoid the fence before re-joining in tenth.
It wasn't over, as Jamie Tilley began applying pressure to Johnson, sliding around the track with a serious slide that he managed to save through Reid Park. Chasing Johnson down Conrod, Tilley lost the rear of the Mustang in even more dramatic fashion as he went around the kink into The Chase, yet this time was unable to save the car, spinning repeatedly before coming to rest on the apex, dropping to 9th.
Fisher looked to fight back from his off with a pass on the XY Falcon of John Adams, but the pair made contact – again at Hell Corner for Fisher, who used the escape road for the second time in as many laps.
With the conditions deteriorating, the race was called at five laps instead of the planned nine, with Pollicina crashing on the final lap at Brock Skyline, the nose of the Torana A9X in the wall with serious front-end damage
While Johnson took a hat-trick of wins over the event, Hansford survived to come home second as title rival Bowe was a non-finisher. Tony Karanfilovski was third from eleventh on the grid, with Adams, Warren Trewin and Cameron Tilley rounding out the top six.