Vettel stuns on BMW debut.

It looks as though Mario Theissen may have stumbled across another precocious young talent after Sebastian Vettel defied his lack of experience in an F1 car and of the Istanbul Park circuit to top the second practice session of the day in Turkey.

BMW Sauber's new third driver, Vettel is in place of the team's new race driver Robert Kubica, with the German wasting little time in impressing the F1 fraternity by ending a faultless day at the top of the timesheets a meagre, but nonetheless significant, seven hundredths up on Felipe Massa.

Naturally, the test drivers will be running additional revs and have more tyres but that does little to take away from the fact that Vettel comes away with the fastest time of the day.

Massa led the charge of the race drivers in second place with a strong late lap, just ahead of Jenson Button, who claimed his second top three position of the day. Compatriot Anthony Davidson meanwhile was fourth quickest, albeit with a new Honda engine fitted following his blow in the morning.

Ralf Schumacher was an encouraging fifth fastest on his first outing of the day, the German faring better than his team-mate Jarno Trulli, who endured a spin on the way to 15th best.

Michael Schumacher was menacing in sixth place having used just a single set of Bridgestone tyres, ahead of the similarly Ferrari powered Red Bull of Robert Doornbos, the Dutchman managing to eliminate his mistakes from the morning to be seventh fastest.

However, he served better than team-mates Christian Klien and David Coulthard, who's lack of running in the morning saw them consigned to a disappointing 22nd and 28th respectively.

Also resisting the temptation to put fresh rubber on their McLaren-Mercedes', Kimi Raikkonen and Pedro de la Rosa were looking solid in eighth and ninth, the Spaniard leading the majority of the session before reverting back to a more conservative program.

Rubens Barrichello was a modest tenth, with Giorgio Mondini representing the advantage provided by new tyres, vaulting from the bottom of the timesheets to eleventh when he put new Michelin rubber on.

Renault's mass damper issues could well be proving more of an issue than they would care to believe, with Fernando Alonso in lowly 12th and once again in dispute with Doornbos, the duo making slight contact on their final laps. Giancarlo Fisichella was an equally worrying 18th.

Neel Jani was the quickest of the Toro Rossos in 13th, ahead of Scott Speed in 14th and Vitantonio Liuzzi 20th, the Italian seemingly struggling to get to grips with the circuit.

A surprise name in mid-field was Franck Montagny, who impressed on his return to Super Aguri with the 16th fastest time, ahead of two BMWs and all three Williams'. Indeed, Robert Kubica and Nick Heidfeld could not match the pace being shown by newcomer Vettel, securing 17th and 27th respectively.

However, at least they fared better than the Williams trio, with Alex Wurz, Mark Webber and Nico Rosberg in 19th, 21st and 23rd respectively, giving them a mountain to climb over the weekend.

MF1 Racing and Super Aguri's drivers rounded out the final positions, with Takuma Sato and Sakon Yamamoto 24th and 25th, while Tiago Monteiro and Christijan Albers claimed 23rd and 29th positions.