Abu Dhabi, United Arab Emirates: Even with his fourth straight Formula One title already secured, there is no easing up from Sebastian Vettel.
The German driver posted the fastest time in the second practice session of the Abu Dhabi Grand Prix on Friday on the Yas Marina circuit, where he secured his first championship in 2010. He clinched his fourth at the Indian GP last weekend with three races to spare.
In cooler evening temperatures, Vettel clocked a best lap of 1 minute, 41.335 seconds to finish .155 ahead of Red Bull teammate Mark Webber and .355 clear of Mercedes driver Lewis Hamilton.
"It's not always so easy at this circuit with the conditions changing throughout the day," Vettel said. "We start in the sun and finish at night and the track temperature changes during that time. But, no big issues, so I'm pretty happy."
Lotus driver Kimi Raikkonen was fourth quickest after narrowly avoiding a crash.
The third practice session is early Saturday afternoon before qualifying in the evening. Vettel has taken pole position in four of the past five races.
Lotus driver Romain Grosjean was fastest in the first practice but the Frenchman struggled with a brake problem in the second and finished 12th.
Grosjean has finished third in each of his past three races and clocked a best lap of 1:44.241 seconds in the first session to finish .192 seconds ahead of Hamilton -- who won the race two years ago and has taken pole position twice -- and .258 clear of Vettel.
"It's difficult to say today how we compare to the others, but we also had decent pace today," Vettel said. "Lotus is exceptionally quick, especially come Sunday, and may be able to pull off strong pace later on in the stint so we will have to keep an eye on them. Mercedes are strong on one lap for tomorrow."
In the second run, Grosjean yelled over the race radio that there was a problem with his front brakes. Although he came back out later in the session, it was a short stint and he had to go back to the pits.
Abu Dhabi is the only race of the year that starts in the late afternoon and ends in the evening.
Because qualifying and the race itself are held at twilight, when the track is considerably cooler at sunset, little useful data could be gained from the first practice.
"The second session is always more valuable here as it's so much more reflective of the race conditions," Hamilton said. "As the temperatures cool down, the characteristics of the car change and you get an increase in understeer, so the main challenge is to try and pre-empt the set-up that you're going to need."
About midway through the first run, Mercedes driver Nico Rosberg locked his front left tire as he broke heavily coming into a chicane and almost slid off the track before regaining control. He had further trouble in the second run, locking his brakes into turn 17.
"It should be an interesting race from a strategy perspective as the tires seem to be right on the limit of one or two stops," Rosberg said.
The Abu Dhabi track has never been much to Ferrari's liking. It was a poor first run for both drivers, with former champion Fernando Alonso in 12th and Felipe Massa in 17th. They fared a bit better in the second session, with Alonso in eighth and Massa 10th.
Nearing the end, Raikkonen almost crashed into Valtteri Bottas as the Williams driver broke late coming into a turn and his car veered left. Then, with a handful of minutes remaining, Raikkonen slid across the track after locking his brakes on turn 17.
