Vettel was fined for pit lane speeding in his first session

The German, 19, clocked one minute 28.091 seconds, 0.073 seconds quicker than Ferrari's Felipe Massa.

Defending champion Fernando Alonso was 12th fastest, with championship rival Michael Schumacher in sixth.

Honda's Jenson Button finished third, while Honda test driver Anthony Davidson was fourth fastest.

Vettel stepped up to become BMW Sauber's test driver as part of the reshuffle which followed Jacques Villeneuve's departure.

In the first session I forgot to press the pit lane speed limiter, which is going to be expensive

Sebastian Vettel

He was fined £500 in morning practice for pit-lane speeding just nine seconds into his debut.

But the teenager ended up third before topping the times in the second session.

"I am surprised at this result," said Vettel.

"It has been difficult for me as I didn't know the circuit and have had only one proper Formula One test.

"My second session was a lot quicker, and on top of that I learnt two Formula One lessons on my first day.

"In the first session I forgot to press the pit lane speed limiter, which is going to be expensive, and after the second session the system chose me for a drug test."

FIVE LIVE VIEW Well done Vettel - a fastest finish when you're only 19 is a bit special

FZ

Button followed up his maiden Grand Prix win in Hungary three weeks ago with another strong showing.

The Englishman was third in both sessions while his compatriot Davidson took fourth and fifth.

"I had a small mechanical problem at the start of the afternoon session, which cost me some time when we had to take the floor off, but everything is okay."

Ferrari ace Schumacher is locked in a tussle with Renault's Alonso for the world championship and arrived in Istanbul just 10 points adrift.

He claimed bragging rights on Friday as Alonso struggled to 12th place after colliding with Robert Doornbos late in the session.

"Today, I have been able to find out how demanding the track is," said Schumacher.

"Last year, we were here with a package that was absolutely not competitive, while today the situation is completely different."

Alonso did not go out in the morning session, with Renault preferring to conserve the engine and tyres on their cars.

"It was a pretty normal Friday for me," said Alonso.

"We tried the tires, did some laps to get comfortable with the circuit again and started to think about the set-up changes for the rest of the weekend."

Kimi Raikkonen, who was fastest in the morning, could only manage eighth in his McLaren in the afternoon session.

Turkish Grand Prix - Friday's combined free practice times

1 S Vettel (Ger) BMW Sauber 1:28.091

2 F Massa (Brz) Ferrari 1:28.164

3 K Raikkonen (Fin) McLaren 1:28.315

4 J Button (GB) Honda 1:28.506

5 A Davidson (GB) Honda 1:28.598

6 R Schumacher (Ger) Toyota 1:28.614

7 M Schumacher (Ger) Ferrari 1:28.777

8 R Doornbos (Ned) Red Bull 1:28.848

9 A Wurz (Aut) Williams 1:28.959

10 R Barrich'lo (Brz) Honda 1:29.214

11 P de la Rosa (Sp) McLaren 1:29.376

12 G Mondini (It) Midland 1:29.719

13 F Alonso (Sp) Renault 1:29.741

14 N Heidfeld (Ger) BMW Sauber 1:29.780

15 N Jani (Swi) Toro Rosso 1:29.858

16 S Speed (US) Toro Rosso 1:29.890

17 J Trulli (It) Toyota 1:30.006

18 F Montagny (Fr) S Aguri 1:30.491

19 R Kubica (Pol) BMW Sauber 1:30.502

20 G Fisichella (It) Renault 1:30.504

21 V Liuzzi (It) Toro Rosso 1:30.551

22 M Webber (Aus) Williams 1:30.775

23 C Klien (Aut) Red Bull 1:30.889

24 N Rosberg (Ger) Williams 1:31.015

25 T Sato (Jpn) S Aguri 1:31.091

26 S Yamamoto (Jpn) S Aguri 1:31.316

27 C Albers (Ned) Midland 1:31.475

28 T Monteiro (Por) Midland 1:31.519

29 D Coulthard (GB) Red Bull 1:31.540