Esteban Gutierrez topped the half hour of free practice ahead of qualifying on Friday for GP2's first ever race around the streets of Singapore.
A heavy thunderstorm in the hour before the session began soaked the track, making conditions perilous with puddles proving slow to evaporate in the humid conditions.
Gutierrez lapped his Lotus GP machine in 2m14.339s, 0.332s quicker than Racing Engineering's Fabio Leimer. Stefano Coletti was third fastest for Rapax, despite overshooting the same corner twice, ahead of Gutierrez's team-mate James Calado and Addax's Johnny Cecotto Jr.
With both championships to be decided this weekend in the season finale, it was Lotus that threw down the gauntlet in the teams' title race - the Paris-based team two points behind fellow French outfit DAMS and very much at the top of the times throughout the session.
Both Calado and Gutierrez are already ruled out of the drivers' title race, however, which will be decided between Davide Valsecchi of DAMS and Luiz Razia of Arden. They remained locked together during the session, but in the lower reaches of the timesheets. Valsecchi ended up 14th and Razia down in 20th.
Valsecchi leads Razia by 25 points, and with four points up for grabs in qualifying tonight, Razia will have to find something special to eat into his rival's advantage.
There were numerous spins, straight-lining of chicanes and overshoots down the escape road, but no actual damage was done during the session. Stephane Richelmi came closest, spinning his Trident car onto the Anderson Bridge but just staying out of the wall.