Lewis Hamilton set the fastest time in the second free practice session at the Nurburgring ahead of Sunday's German Grand Prix.

It was the third time this season that the 24-year-old Englishman had been quickest on the opening day in his McLaren Mercedes, having been fastest previously on Friday in Bahrain and China.

Heikki Kovalainen, his McLaren team-mate, however struggled to 17th place on a cool, wet day.

Hamilton clocked a best time of one minute and 32.149 seconds with six minutes of the 90 remaining to ease clear of Sebastian Vettel, in his Red Bull, by two-tenths of a second.

Jenson Button, the drivers' championship leader, was third for Brawn GP ahead of Mark Webber, in the second Red Bull, with Jarno Trulli fifth for Toyota and Adrian Sutil sixth for Force India.

Rubens Barrichello, Button's Brawn team-mate, was seventh ahead of Renault's Fernando Alonso. The two Ferraris of Felipe Massa and Kimi Raikkonen were 12th and 16th, unable to match the pace-setters on a dismal day for them and many of the spectators as the weather took its toll in the Eiffel mountains.

The afternoon session was punctuated by rainfall and the conditions were more favourable to the Red Bulls than Brawn as the track temperature crept slowly up from 16C in the morning to 24C in the afternoon.

After early drizzle, Kovalainen took the top spot for McLaren Mercedes - a rare occurrence this season - before Webber took command for Red Bull. Button then took over at the top before Vettel, 66 minutes into the 90, took over as the fastest man only to be eclipsed by Hamilton.

Earlier, Webber topped the times in the morning's opening free practice, narrowly outpacing Button. Their duel was a prelude to the afternoon session which, in itself, suggested that McLaren may have made a performance leap - but without disguising the more likely fact that it this weekend's contest will be between the Brawns and Red Bulls again with Button and Vettel leading the way.