Mercedes dominated practice at the Malaysia Grand Prix on Friday with Lewis Hamilton and Nico Rosberg going fastest in one session each.
Since the mid-season break, Rosberg has won all three races to regain the standings lead from his team-mate, and his race weekend started well as he topped the timesheets in the first session in a sweltering Kuala Lumpur.
That session saw Kevin Magnussen's Renault catch fire following a fuel leak, although the Dane was able to escape unscathed and returned for FP2.
Hamilton - who claimed pole last year - then took charge in the second session, posting the fastest lap with a time of one minute 34.944 seconds, 0.233secs ahead of his team-mate, while Ferrari's Sebastian Vettel was third quickest.
Vettel, victor at this circuit in 2015, was pleased with the way his day had gone.
"It was a decent day, we tested quite a few things," he told reporters.
"Historically we seem to do well when it's warm. We tried to be competitive, out there it's difficult, so if the conditions suit us it might be a good thing.
"We hope we can improve, but whatever comes we need to take it. Our target is to win a race or more than one if we get a chance. We'll do our best and see where it takes us."