Welcome to commentary for the third and final practice session at Istanbul Park. There is barely a cloud in the sky this morning over the circuit and over the next hour or so the teams will be keen to get out on track and refine their setups ahead of the all-important qualifying session this afternoon.

The drivers are being strapped in to their cars, we're now just moments from the start of this session. Air temperature is 14C and track temperature is 27C.

Vettel's car has been fully fixed overnight, so he'll be keen to make up for lost time this morning after he missed out on all the dry running yesterday due to an accident in FP1.

And Vettel is the first man out of the pits on hard tyres. He'll complete a quick installation lap come back to the pits and then start setting the car up for qualifying and the race. He's got Webber's data from yesterday so isn't going into this session completely blind.

The two McLarens are also out as well as Webber.

The Ferraris are ready to leave the pits. Both cars are running the new rear and front wing as well as the upgraded brake ducts the team has brought to the track this weekend. Yesterday Pat Fry said the rear wing gave instant results but the front wing wasn't quite working how they expected.

Petrov breaks the trend with two installation laps before returning to the pits. Everybody else has completed one.

There's a bit of a mop up and top up job going on in the Lotus garage on Trulli's car. The mechanics are also taking a look at the back of the car with flashlights.

Ferrari says: "Both drivers are back in the garage, nothing specific to report."

Tom from Melbourne asks: "Does the 'aero paint' that one team runs (for example Webber for RBR at the moment) give away many clues for other teams who are watching? Does it give away the cars aerodynamics?"

Yep it does to an extent. There are plenty of teams with photographers in the pit lane to get snaps of their rivals. To analyse it properly, however, it is better to get the car in the garage and have a close look. McLaren used to run UV paint that you could only see under a UV light back in the garage, but they don't seem to bother any more.

D'Ambrosio is the only man out on track, he's having to lift quite a lot in turn eight. It will be interesting to see if the Red Bull's take that flatout in qualifying as they did last year.

Mercedes' agenda for the morning: "This morning's plan will be to check the balance and set-up following work overnight and complete the tyre evaluatons ahead of qualifying."

D'Ambrosio is the only man to set a time so far with a 1:33.312 and is running the new nose cone on the car.

More cars are now filtering out of the pits. Button is on a timed lap and Schumacher has just set a new fastest time with a 1:27.619.

Button's time is 0.796 off Schumacher's but it's still early in this session and we've only seen hard tyre runs so far. Vettel is now out on track but is not on a particularly special lap.

Rosberg goes quickest with a 1:27.358, 0.2 faster than Hamilton's most recent effort.

Karthikeyan is fighting his car all around the circuit and is currently 0.4 seconds off team-mate Liuzzi.

Alguersuari has spun off at turn three, we haven't seen what happened yet but it's a strange place to go off. He's out of the car which doesn't look too badly damaged but has stalled and his session is probably over.

Ferrari says: "Fernando is going out now. Both drivers on hard tyres, as usual for FP3 first run"

Vettel is now fastest with a 1:27.134, 0.224 seconds faster than Rosberg. It hasn't taken long for the world champion to get up to speed.

Webber goes third fastest after getting stuck behind a Virgin in the final corners.

Petrov has popped up to fourth fastest, 0.332 off Vettel. Yesterday he was pleased with the car and said he expected to be even quicker today.

Massa trundles back to the pits after the car looked horrible under braking for turn 12. I'm not sure Ferrari's updates have done the job this weekend and it seems as though they will be fighting Renault and Mercedes rather than McLaren and Red Bull this weekend.

Turkey last year was a terrible race for Ferrari and Alonso failed to make the cut for Q3. They managed to turn their form around towards the end of the season and they are hpoing they can do the same this year.

We're still waiting for our first soft tyre runs. Vettel is still fastest with a 1:27.134.

Alguersuari's car has been pushed back to the pits so we might yet see him back on track in this session.

Rosberg holds a ridiculous slide through turn eight and ends up cutting the second apex. Remakably he held it all together and carried on with his lap.

Bruno asks: "How come some drivers stay in pit long after FP3 has opened instead of taking full advantage of the 60 minutes available?"

The main limiting factor is tyres. The drivers have one set of hards and one set of softs for this session so can probably only do 25-30 laps maximum. But they also don't want to put unnecessary mileage on the engine. If they are happy with the setup then there is no need to go out over and over again. Trying to find a setup on worn tyres can also be misleading so once the tyres start to drop off they are fairly useless unless you are working on race startegy.

We're seeing the first soft tyre runs and Massa has used his fresh set to go fastest with a 1:26.883. Meanwhile Vettel improves to a 1:26.940 on his set of old hard tyres.

Vettel is not using his KERS at the moment. That could indicate a problem and he returns to the pits.

Massa runs wide into turn nine as his soft tyres start to drop off after three laps.

Alonso goes fastest with a 1:26.819 on the soft tyres. He's 0.064 up on Massa so there isn't much to choose between the two Ferraris this weekend.

Rosberg is now on the soft tyres and set for the fastest lap as he comes out of sector two... and he gets the fastest lap with a 1:26.446.

Schumacher pips his Mercedes team-mate with a 1:26.038 despit a slightly scrappy end to the lap. The Mercedes looks quick this weekend, but expect the McLarens and Red Bulls to put in competitive times before the end of this session.

Alonso's Ferrari is stuck in sixth gear, possibly a repeat of the hydraulics issues he had on Friday.

Button can only manage third fastest, 0.540 off Schumacher and Hamilton's soft tyre lap is only good enough for fourth.

Ferrari says: "Fernando is back complaining for some apparent loss of power. Now we check the car to see if there is something wrong."

The BBC reports that Vettel's KERS problem was down to a cooling issue. They're making adjustments to get him out again in this session.

In fact Vettel is on track right now on the soft tyres. His team-mate Webber is on track on the soft tyres but not as quick as Schumacher.

Webber goes third fastest, 0.438 off Schumacher. Webber's KERS was working.

Vettel starts his flying lap on the soft tyres... he's 0.043 off Schumacher through sector one... 0.297 up through sector two which covers the fast turn eight... and he goes 0.001 faster than Schumacher but the end of Vettel's lap was hampered by Liuzzi's HRT.

Webber pops up to third fastest on his slightly used soft tyres, he was 0.367 off team-mate Vettel.

The session has ended and nobody is on a quick lap so Vettel's time looks safe.

Just 0.001 separated Vettel and Schumacher at the end of the session, but Vettel will be capable of much more without a HRT in front of him through the final three corners.

But a good result for Mercedes and they will go into qualifying with their heads held high.

At the back of the grid Karthikeyan just snuck within 107% by 0.050 seconds, but thr fornt runners won't use the soft tyres in Q1 so HRT are probably safe. Meanwhile, Liuzzi got within 0,2 seconds of the Virgin of Glock.

Thank you for joining us for the final practice session. Make sure you check back in two hour's time for the all-important qualifying hour.