Lewis Hamilton led the way on Thursday's rain-hit third day of testing at Sepang, as changeable weather conditions left drivers and teams frustrated.
An overnight downpour meant the track was soaked for the start of the day and, although it eventually dried up just before lunch, another shower late in the afternoon meant there was only a few hours for drivers to set their best laps.
Hamilton stopped on the track once with an oil leak just after 12pm, but soon got further acclimatized to the Sepang circuit to set a best lap that was two tenths of a second faster than Mark Webber's Red Bull Racing car.
Ralf Schumacher was third quickest for Toyota, while Scuderia Toro Rosso's Vitantonio Liuzzi was just one hundredth of a second behind him.
Felipe Massa, taking over duties from Kimi Raikkonen, was fifth fastest ahead of Nico Rosberg in the Williams and Jenson Button in the Honda - who completed a mammoth 92 laps.
Behind eighth fastest Anthony Davidson in the Super Aguri, Nick Heidfeld had the most dramatic day as his car stopped on track in the morning with an oil leak - which promptly caught fire and damaged the bodywork.
With the mixed conditions limiting dry running today, the teams have decided to extend the test for another day.
Pos Driver Team Times Laps 1. Hamilton McLaren-Mercedes (B) 1:35.918 57 2. Webber Red Bull-Renault (B) 1:36.138 62 3. R.Schumacher Toyota (B) 1:36.700 69 4. Liuzzi Toro Rosso-Ferrari (B) 1:36.712 56 5. Massa Ferrari (B) 1:36.947 64 6. Rosberg Williams-Toyota (B) 1:37.070 71 7. Button Honda (B) 1:37.472 92 8. Davidson Super Aguri-Honda (B) 1:37.606 44 9. Heidfeld BMW Sauber (B) 1:38.551 35 10. Kovalainen Renault (B) 1:39.654 20 All timing unofficial