Ahead of this morning's all important practice session, the air temperature is 14 degrees C, while the track temperature is 26 degrees. After yesterday's mixed conditions, wet in the morning and dry in the afternoon, it is altogether better today with the Istanbul Park Circuit bathed in warm sunshine.

Jenson Button was quickest in yesterday afternoon's session, with teammate Lewis Hamilton confirming McLaren's pace by finishing third. However, the Woking duo have admitted to being concerned not only by the obvious favourites, Red Bull, but by the ever improving Mercedes, Renaults and Ferraris. Indeed, at a time when almost all the teams are running significant upgrades, both McLaren drivers are concerned at the lack of new bits on their cars.

Following a hefty crash in the first session, and having taken the blame, Vettel says he isn't unduly worried at having had no running in the afternoon, though teammate Mark Webber's pace indicates that the Milton Keynes team should be good here.

Other than the big four, Force India is looking good to continue its points scoring run here, while Williams continues to struggle.

Tyre options this weekend are, once again, hard (prime) and soft (option). Thus far, wear hasn't been as excessive as expected.

The lights go green and d'Ambrosio leads the way, followed by Trulli, di Resta, Liuzzi, Alguersuari and Vettel, the German keen to make up for lost time.

Both Ferraris are running new front and rear wings together with new brake ducts. The Italian team is looking for a major improvement this weekend.

While most drivers return to the pits following their installation lap, Petrov stays out. A number of cars feature the luminous flow-viz paint as teams continue their quest to learn.

Ten minutes into the session d'Ambrosio is back on track, the Belgian having picked up a grid penalty for ignoring a yellow flag during yesterday afternoon's session.

The Virgin driver crosses the line at 1:34.464, the Belgian making good use of the new nose which was only available to teammate Glock yesterday.

As d'Ambrosio improves with a 32.603, he is joined by Liuzzi, Karthikeyan, Kobayashi, Schumacher, Kovalainen, Hamilton, Button and Rosberg.

Schumacher posts 27.619 to go quickest, leaving d'Ambrosio almost 5s behind. Button subsequently goes second (28.415), ahead of Kobayashi, Kovalainen and Rosberg.

As Rosberg goes quickest with a 27.358, the session end for Alguersuari who has gone off at Turn 3. The Spaniard climbs from his car and begins the long walk back to the pits.

Hamilton improves to second (27.548), as Vettel posts 27.791 to go fifth. Next time around, and despite the lack of previous running, the world champion goes quickest with a 27.134. Business as usual.

Having had a spin, Webber goes quickest in S1 as he seeks to improve on sixth (27.853). However, running wide in S3 to avoid Glock's Virgin, the Australian can only manage 27.391 which puts him third.

Petrov improves to fourth (27.466) as Heidfeld seeks to improve from ninth.

At half-time, it's: Vettel, Rosberg, Webber, Petrov, Hamilton, Schumacher, Button, Alonso, Heidfeld and Buemi.

As he attempts to close the gap to Vettel, Rosberg gets well and truly out of shape. Elsewhere, a major lock-up for Liuzzi.

With 23:00 on the clock, Alonso is eighth and teammate Massa eleventh, both over 0.8s off the pace.

Another hairy moment for Rosberg, the German doing a brilliant job holding the Mercedes as it attempts to snap out of shape in the notorious Turn 8.

Vettel goes quickest in S2, however, a relatively poor final sector sees him fail to improve. No such troubles for Buemi however, the Swiss posting a 27.080 to take the top spot, no doubt spurred on by his soft tyres and the presence of Daniel Ricciardo.