Red Bull's Sebastian Vettel headed Ferrari's Felipe Massa in the first practice session of the new season at the Australian Grand Prix.
The world champion was just 0.078 seconds quicker than the Brazilian in a closely matched session that hinted at a competitive season ahead.
Ferrari's Fernando Alonso was third, 0.366secs off Vettel, with the Mercedes of Lewis Hamilton in fourth.
Red Bull's Mark Webber was fifth ahead of Lotus driver Kimi Raikkonen.
The session, inconclusive though it was, suggested that four teams will be fighting it out at the front initially - with Red Bull, Ferrari, Mercedes and Lotus closely matched.
Pre-season testing had suggested McLaren were struggling for pace and the first session in Melbourne's Albert Park seemed to confirm that.
Jenson Button, who has won this race for three of the last four seasons, was only ninth fastest, behind the second Mercedes of Nico Rosberg and Adrian Sutil's Force India and 1.229secs off the pace.
Button's new team-mate Sergio Perez was close behind in 11th place, with Lotus's Romain Grosjean splitting the two McLarens.
The Sauber of Nico Hulkenberg was 12th, ahead of Scot Paul di Resta, who was nearly half a second slower than Sutil.
Di Resta ended the session in the gravel trap after spinning at Turn Six.
Massa also provided some entertainment, with some spectacular slides in the Ferrari.
At the back there was an impressive performance from Marussia's Jules Bianchi, who was nearly a second faster than team-mate Max Chilton and just 0.3secs off the Toro Rosso of Daniel Ricciardo.
The second session, which starts at 0530 GMT, should provide further clues to the competitive order.
The forecast for qualifying on Saturday is for rain, which could provide a mixed-up grid ahead of an expected dry race on Sunday.