Red Bull's Sebastian Vettel set the pace in the Friday practice session in Singapore.
The current world champion narrowly beat Ferrari's Fernando Alonso and McLaren's Lewis Hamilton ahead of qualifying on Saturday.
Hamilton was fastest in the first practice, but fell behind Vettel in the second and third sessions, while teammate Jenson Button missed half of the afternoon after going off the track.
Vettel leads the standings by 112 points and can retain his title this weekend if results go his way.
