Istanbul - Ferrari underlined their position as favourites to win the Turkish Grand Prix after defending champion Kimi Raikkonen and team-mate Felipe Massa won both of Friday's two practice sessions. Finnish driver Raikkonen set the pace in the day's second session after Brazilian Massa was fastest in the morning.
Raikkonen appeared only briefly in the first session after suffering a gearbox problem, but returned in the afternoon to set a fastest time of 1 minute 27.543 seconds.
Lewis Hamilton, third behind McLaren-Mercedes team-mate Heikki Kovalainen in the first session, was then second fastest in the afternoon in 1:27.579, with Massa (1:27.682) third.
David Coulthard (Red Bull), Kovalainen, Robert Kubica (BMW-Sauber), Jarno Trulli (Toyota) and Kazuki Nakajima (Williams) made up the top eight places
Massa, bidding for a third straight win in Turkey, was fastest of the day with a best lap of 1:27.323 at the 5.339-kilometre Istanbul Park circuit.
That was enough in the morning session for a 0.133-second lead over Kovalainen, who was returning to the track for the first time since suffering concussion in a crash at the Spanish Grand Prix.
The practice sessions are mainly used by teams to determine the set-ups of their cars ahead of Saturday's qualification which will determine grid position for the fifth Formula One race of the season.
"As far as the absolute best time is concerned I wouldn't take it too seriously," said Mercedes sports chief Norbert Haug.
"All in all we have a reasonable basis without saying we have Ferrari under control.
"The most important thing is that Heikki is back in the car and was immediately fully into it. He's just like he was. That is the best thing about today."
Elsewhere, Renault's two-time world champion Fernando Alonso of Spain, who was fourth fastest in the morning, settled for ninth in the afternoon.
Coulthard's Red Bull team-mate Mark Webber missed most of the second session when he crashed his car after running off the track.
Force India driver Giancarlo Fisichella was handed a three-place grid penalty for ignoring a red light at the exit of the pit lane in the first session.
Formula One has meanwhile changed its qualifying rules after the withdrawal of the Super Aguri team from the championship because of a lack of funding.
With 20 cars from 10 teams now in the starting line-up, organizers have decided that five cars instead of six will be eliminated at the end of each of the first two parts of qualifying.
Ten cars will still race for pole position in the final 10-minute phase.
Raikkonen, who won in Spain two weeks ago, leads the drivers' standings on 29 points, with Hamilton on 20 and Kubica on 19.
Ferrari lead the constructors' standings with 47 points, 12 more than BMW-Sauber and 13 more than McLaren.
