Mercedes driver Lewis Hamilton set the pace from Ferrari's Kimi Raikkonen in first practice at the Malaysian Grand Prix.
Hamilton, one of several drivers to have off-track moments, was 0.152 seconds ahead of the Finn, with the second Mercedes of Nico Rosberg third.
McLaren drivers Jenson Button and Kevin Magnussen were fourth and fifth.
World champion Sebastian Vettel was seventh for Red Bull and Ferrari's Fernando Alonso 11th after a spin.
Hamilton was 0.337secs quicker than Rosberg and Raikkonen 1.08secs ahead of Alonso.
The Spaniard was fastest after the first runs, but failed to improve after that.
Alonso had an uncharacteristic spin at Turn Eight with half an hour of the session remaining. It damaged a rear tyre and the floor, and with no time to repair the car the team concentrated on systems checks and practice starts for the remainder of the session.
It was an unusually incident-packed first 90 minutes of action, as drivers got to grips with the challenging Sepang track in the new 2014 cars, which have less downforce than last year and more torque and power from the engines.
Alonso's former team-mate Felipe Massa, now at Williams, repeated the error few minutes later.
Hamilton ran wide on the entry to Turn 11 after running on to the outside kerb whilst making his way into the corner, afterwards complaining of 'marbles' - tyre debris on the track making it slippery.
Sauber's Adrian Sutil spun on his way into the pits after putting his right rear wheel on the grass on the way in, and Caterham's Marcus Ericsson spun at the final corner on one of his laps.
Raikkonen came very close to a spin, with a big wobble into Turn 11.
And Rosberg almost lost control on his way into the pit lane as he braked down to the point where the speed limit starts.
Lotus' troubled start to the season continued as Romain Grosjean stopped on track with a problem connected to the charging of the batteries from the hybrid system.
The Franco-Swiss did get out later in the session but failed to set a time.
Team-mate Pastor Maldonado managed only an installation lap and a warm-up lap before his car stopped with blue smoke coming from the rear.
Lotus are still struggling with reliability problems caused by being under-prepared for the start of the season because their car programme was late, a knock-on effect of budget problems suffered through 2013.