Jenson Button on Tuesday got a taste of V8 Supercar racing when he swapped his McLaren for a Holden Commodore of the Australian touring car series.
In a Vodafone sponsor event, the 30-year-old did a few laps of the Albert Park circuit in fellow reigning champion Jamie Whincup's car.
But while Briton Button enthused about the "quite good" Supercar, 27-year-old Whincup could not stop saying the word "unbelievable" when he emerged from the 2008 McLaren, which was fitted with grooved Bridgestone tyres.
"It was unbelievable, I can't really explain it," said the Australian, who said driving an F1 car had been one of his three dreams, including flying a fighter jet and travelling into space.
"The car just does everything right," he added, albeit acknowledging that he braked too early for the corners.
"The strain on my head was unbelievable. I don't get anywhere near the Gs in my car -- the acceleration and the braking, I've never felt anything like it before.
"I've got huge respect for these guys. To do a full grand prix at that pace is unbelievable," said Whincup.
It was a mild, windy and overcast day in Melbourne on Tuesday, but although the clouds are likely to stay overhead this week, rain is unlikely.
Button's team is expecting a more competitive weekend than in Bahrain, but he admits that two other teams are leading the pace at present.
"You'd have to say the Red Bulls are very strong. The Red Bulls and the Ferraris were so quick in Bahrain," he said.