Highlights - Australian GP second practice
By Julian Shea and Mike Henson
McLaren's Lewis Hamilton took advantage of some rare dry conditions in the second session to clock Friday's fastest practice time in Melbourne.
Hamilton set a lap of one minute 25.801 seconds to edge out team-mate Jenson Button by 0.275 secs before a spell of heavy rain hit the Albert Park track.
Red Bull's Mark Webber emerged as the track dried later on to go third ahead of Mercedes's Michael Schumacher.
Renault's Robert Kubica was fastest in the day's first practice session.
"It's definitely not the weather I am used to in Australia, but we did get some dry running which is not too bad," said Hamilton.
"The track was very dirty in the first session, everyone just waits forever to go out and I wanted to go out and have some fun, so I went out early.
"Generally the session was quite good. I had to make some changes to the car but I did that in between sessions.
"It was difficult at the end when we made some more changes as the track was not up to top speed. Nevertheless we felt quite comfortable with the balance of the car so I am quite happy."
With temperatures lower than in the first session and light rain falling, there was little action for the opening part of the second 90-minute session as the pit crews switched their attention to the weather and weighed up swapping dry-weather slick tyres for intermediates.
Hamilton not hampered by rain
The BMW Sauber pair of Pedro de la Rosa and Kamui Kobayashi were among the first to go out, but they struggled for grip.
But the rain eased off and the Williams duo of Rubens Barrichello and Nico Hulkenberg posted the first times after 16 minutes.
The McLaren drivers then vied for the lead, with the 2008 champion responding after his successor had stolen ahead.
Button pushed hard to strike back but could not match his colleague and the two McLarens stayed at the top of the times for the rest of the session as the rain came and went.
It is tough with a big difference in speed and we are one of the quicker cars at the moment
The track dried in the closing minutes of the session, allowing Michael Schumacher to depose Russian novice Vitaly Petrov's Renault from third spot before the seven-time champion was himself beaten by Red Bull's Webber.
The Australian's team-mate Sebastian Vettel ended the session 16th fastest, sandwiched between the Ferraris of Bahrain winner Fernando Alonso and Felipe Massa as all three appeared to concentrate on race preparation with heavy fuel loads.
After his short-lived debut at Bahrain, Karun Chandhok's Hispania had to be pushed back to the pit lane by the marshals after a suspected gearbox failure left it stranded on the track.
There was more drama right at the end as De la Rosa narrowly avoided collisions as he was overtaken by both Button and Hamilton.
"As soon as I jumped in the car, I was reasonably happy with the balance and it's just got better throughout the day," said Button.
"It is so busy that it is difficult to get a gap but our cars are running well around here so it is positive in that way. The last couple of laps were frustrating.
Vettel anticipates qualifying 'traffic'
"I think some cars are not being told the correct information about us catching them up.
"I know it is tough with a big difference in speed and we are one of the quicker cars at the moment, but we will forget about that and just focus on making sure it is competitive tomorrow."
One of those struggling outfits, Virgin Racing, suffered badly from technical problems as a gearbox leakage and telemetry problems blighted Lucas di Grassi and Timo Glock's second sessions.
It was a further blow to the team, who it has emerged are having to redesign their car after discovering the fuel tank is too small to get them to the end of races at full speed.
Kubica was 11th in the second session after setting the pace in the first session with a fastest lap of 1:26.927, 0.199secs ahead of Mercedes' Nico Rosberg.
The German was 0.356secs ahead of Button's McLaren in third, with Massa, Vettel, Alonso and Hamilton were next up.
Force India reserve driver Paul di Resta, who drove the session in place of regular driver Adrian Sutil, was a creditable 11th on his Formula 1 race-weekend debut, one place ahead of Schumacher's Mercedes.