Mercedes' team boss Toto Wolff admits he is struggling to work out why the W08 car has "underperformed" this season.
Mercedes' three-time world champion Lewis Hamilton leads the drivers' standings by 34 points with five races of the season to go, while the Brackley-based team also top the constructors' championship by a margin of 118 points.
But Wolff says he cannot explain Mercedes' inconsistency in the previous two races in Singapore and Malaysia.
Red Bull's Max Verstappen beat Hamilton into second place at Sunday's Malaysian Grand Prix, while Ferrari's Sebastian Vettel, who had started in last place after engine problems prevented him from setting a time in Saturday's qualifying, stormed through the field at the Sepang International Circuit to finish fourth.
In Singapore, Hamilton only finished fifth in qualifying, but still won the race at the Marina Bay circuit on 17 September after Verstappen and the Ferrari pair of Vettel and Kimi Raikkonen crashed at the first corner.
"Full credit to Red Bull and Ferrari for their performance [in Malaysia], but we have underperformed in Singapore and Kuala Lumpur - this is what we need to concentrate on," Wolff said.
"I think we have built a points advantage to Ferrari in the last two races because of them shunting out in Singapore and Sebastian's engine problems here in qualifying.
"If they had performed as they should have we would not have increased our points advantage but lost many points to them.
"We need to understand why we underperform on certain circuits and in certain ambient conditions.
"I think we have a capricious car that has a very narrow operating window with the tyres. Dipping in and out of the window is the fundamental story of 2017 for us."
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