Michael Schumacher and Lewis Hamilton were at the top of the timesheets Friday in damp practice sessions for the Chinese Grand Prix, with Vitaly Petrov 20th fastest.
The Mercedes of Schumacher was two-tenths of a second ahead of the Briton, who has started the first two races of the season from pole position but has a five-place grid penalty in Shanghai for an illegal gearbox change.
The German's speed on the track was aided by a controversial rear wing design, which Lotus unsuccessfully appealed against as illegal against this week.
Reigning champion Sebastian Vettel was third, ahead of Red Bull teammate Mark Webber in fourth.
There was continuing disappointment for Ferrari as Fernando Alonso clocked a time 1.3 seconds off the pace in tenth, while Felipe Massa was a further second back.
Petrov, meanwhile, showed consistency, albeit as a back marker.
"I had a slightly interrupted session this afternoon with maybe one run lost to an alteration to the front suspension early in the session," he said on comments on Caterham's site.
"With some hard work tonight I think we can be ok for tomorrow and the race on Sunday."
The Russian has qualified in 20th and 19th for the first two Grand Prix of the season so far. He crashed out of the season-opener in Melbourne, Australia, with steering trouble, but finished 16th at the team's home race in Malaysia.
