Germany's Nick Heidfeld was quickest in Formula One testing in his BMW-Sauber at the Montmelo circuit in Spain, recording the fastest time from Kimi Raikkonen of Ferrari and Jarno Trulli in his Toyota.
Briton Jenson Button was fourth-fastest on the day in his Brawn GP.
Button did 82 laps with the team having just been unveiled last week after Ross Brawn stepped into the breach after saving Honda from F1 extinction.
The Brawn GP team, with experienced drivers Button and Rubens Barrichello at the wheel, is now playing catch-up with its rivals but Button's debut showing in the distinctive black, white and yellow BGP 001 car powered by a new Mercedes-Benz engine will have been cause for optimism
