Britain's Lewis Hamilton and Formula One champion Jenson Button led a McLaren one-two at the top of the timesheets in first free practice for the Turkish Grand Prix today.
Hamilton, the 2008 champion, was nearly a second quicker than his compatriot with a best lap of one minute 28.653 seconds around the undulating anti-clockwise Istanbul Park track to the Asian side of the city.
Button, last year's winner in Turkey with what he described then as a 'monster' of a Brawn, was 0.962 slower with seven times world champion Michael Schumacher third for Mercedes with a time 1.097 slower than Hamilton's.
The German was followed by two compatriots, team mate Nico Rosberg and Red Bull's Sebastian Vettel, who was 1.2 seconds off the leading pace.
Friday was Vettel's first chance to try out a different chassis, dubbed 'Randy Mandy' and used previously only in pre-season testing, at a grand prix weekend after a defect was discovered in the car he had used for the past six races.
Friday practice is more morale-boosting than indicative of true performance however, although Red Bull's championship leader Mark Webber warned on Thursday that the McLarens could be a real threat.
"We saw in Barcelona that things were a little bit different," the Australian, who is level with Vettel on 78 points after six races, reminded reporters.
"Lewis was our closest competitor in that Grand Prix, so you can argue that if we had a Turkish Grand Prix after Barcelona, you might say that the McLaren might be the guys that might be our challengers here.
"But we're also mindful of the fact that Ferrari, and also if Mercedes have a clean weekend, there's lots of guys that can come towards us, so we're definitely not taking anything for granted," he added.
Webber, winner of the last two races at the fast Spanish track and then on the winding streets of Monaco, was eighth fastest.
Ferrari's Fernando Alonso, third in the championship ahead of his team's 800th race, was ninth.
Force India's German Adrian Sutil had the only accident of the session, the German losing control through the difficult Turn Eight in the closing minutes and spinning into the barriers.
Brazilian Bruno Senna sat out morning practice for HRT, his place going to test driver Sakon Yamamoto. The Japanese was 7.4 seconds off the pace and more than a second slower than Indian Karun Chandhok in the other HRT.