The next best car was the #222 Valvoline Audi, Kelvin van der Linde's time eight-tenths down on van Gisbergen's benchmark.
However, as good as the T8 one-two looks on paper, van Gisbergen isn't expecting the advantage to carry over into qualifying.
He reckons both the locally-run Mercedes put their best foot forward during that final practice with a full qualifying simulation, while the rest of the field were sandbagging ahead of tomorrow's running.
“Our team is doing a great job with the car, but it’s an unknown, because we’re probably the only ones not sandbagging," he told Motorsport.com.
“Tomorrow, everyone will turn up, but this is a good start for us. We’re tapped out, pretty much. I think others will get quicker.”
Van Gisbergen added that he struggled in the hot conditions, which saw temperatures peak at 39 degrees celsius, particularly as he wasn't running the in-car air-conditioning during flying laps.
“I don’t really like Australia at this time of year. I wish I was back at home in New Zealand," he said.
“[The air-conditioning] is worth about four to six-tenths per lap, so [team boss] Roland [Dane] won’t let me run it! We’re all struggling, but on the out laps and in laps, we put it on to cool down for our runs.”