Nico Rosberg has revealed Mercedes suffered with higher than expected tyre degradation in Friday's practices at the Sepang circuit.
Although the Mercedes driver finished Friday's running at the top of the timesheets with a 1:39.909, like many of his rivals he struggled in the heat.
Following on from his hot lap, Rosberg embarked on a longer stint where the German soon found himself dropping with each passing lap as his tyres degraded.
"It was crazy conditions out there," he said. "In the very, very warm temperatures, it's a huge challenge to get everything right.
"The cars are on the edge and the tyre degradation was higher than expected today - we are sliding a bit more this year, perhaps because of the reduced downforce levels.
"We are still having some small issues and therefore we were not able to maximize everything today."
Rosberg's lead, though, wasn't much as Kimi Raikkonen finished just 0.035s behind while the top seven were separated by less than four tenths.
"The quickest teams seem to be closer together than in Australia, so we still have work to do overnight to improve our level of performance."