Sergio Perez laid down a marker ahead of this afternoon's GP2 Series qualifying session at Valencia by going quickest in free practice this morning.
The Barwa Addax driver managed a best time of 1m46.670sec, enough to put him 0.245sec clear of second-placed Pastor Maldonado, although the gap would likely have been smaller if Davide Valsecchi hadn't encountered yellow flags in the final sector during his last flying lap.
The Italian had been 0.1sec off Perez at the end of sector two, but was forced to back off for the last couple of corners.
It was a tough start to the weekend for Racing Engineering's Dani Clos, who broke down on the pit exit at the start of the session and failed to complete a lap.
ART's Sam Bird must go into qualifying with just three laps under his belt after clouting a barrier and ripping off his rear wing.