Reigning world champion Lewis Hamilton returned to the wheel of his new McLaren yesterday and immediately set the pace in testing at Jerez.
Taking over from Heikki Kovalainen, Hamilton posted the best time this week of the '09 spec cars on view at the circuit in southern Spain.
But Hamilton was pushed to the limit by Sebastian Vettel in his Red Bull, with the young German again suggesting he and his team could give McLaren and Ferrari a run for their money in the title race.
Hamilton completed 93 laps, with his best a one minute 20.737secs, only one thousandth of a second quicker than Vettel.
Hamilton was happy enough with the progress of the car, and said: "Today's test gave me the first opportunity to drive it in warm, dry conditions, and I'm very encouraged by what I felt.
"The car feels strong, very similar to last year's car, in fact.
"It doesn't take long to get used to the new buttons in the cockpit (KERS & front-wing flaps).
"But the real test for everyone now is to understand the slick tyres ahead of the first race in Melbourne next month."
Williams' Kazuki Nakajima was in close attendance as he finished 0.161secs down on Hamilton, with Renault's Fernando Alonso just over four tenths of a second further back.
Alonso racked up an astonishing 133 laps, and at least offered his team some encouragement by closing the gap to the front-runner to under 0.6secs - Nelson Piquet Jnr had finished the first two days more than a second off the pace.
At the top of the timesheets overall was Sebastien Bourdais on his first day back at work for Toro Rosso after recently re-signing for a second season with the team.
The Frenchman, though, was running in last year's car, which is due to have its final outing tomorrow, clocking up 126 laps and finishing more than 2.2secs ahead of Hamilton.