British GP: Nico Rosberg quickest at Silverstone, Paul Di Resta fourth
Mercedes' Nico Rosberg set the pace from Red Bull's Mark Webber in Friday practice at the British Grand Prix.
Rosberg, who has taken pole position in three of the last four races, was 0.299 seconds ahead of Webber, who is leaving Formula 1 at the end of the season.
Webber's team-mate Sebastian Vettel was third, 0.432secs behind Rosberg, with Force India's Paul Di Resta and Mercedes' Lewis Hamilton next.
Title contenders Fernando Alonso and Kimi Raikkonen were 10th and 13th.
They both looked more competitive on the race-simulation runs later in the session, but the mixed conditions of the day ensured the picture was harder to read than normal.
The second session started on a wet track after morning rain rendered the first effectively worthless and the team's compressed their normal programmes into one 90-minute session.
That meant the teams did not complete their normal one-lap qualifying simulation runs on the faster tyre, preferring to focus on ensuring their cars had the best set-up.
"Overall we can be pretty happy," said Vettel. "It was a good day. It was important to get some laps in the dry because we expect it to be dry on Sunday.
"Now we need to look a bit closer at what we did and what the others did, try to improve - we need to improve a little bit here and there - and then we will know a little bit more for tomorrow."
BBC 5 live analyst and former F1 driver Allan McNish said: "It is a familiar picture. The Mercedes are very fast in all conditions and Webber appears to be ahead of Vettel on one-lap pace.
"Vettel has been very strong on the longer runs. Alonso has been fast but I need to see a bit more from him. Raikkonen right now is probably the dark horse in that we don't know if he's got the pace in qualifying conditions but he looks good in race trim."
Mercedes have suffered from heavy tyre usage in races so far this season but on the evidence of Friday they are in better shape on that front - with their lap-time averages over their long runs comparable with those of Red Bull and Ferrari.
Lotus's Romain Grosjean appeared to be in the best shape in race trim but that could be the result of a lower fuel load, the sizes of which the teams do not publish.
Ferrari suffered a blow when Felipe Massa spun at the exit of Stowe early in the session, damaging the nose of his car and ending his session after less than half an hour.
The accident meant the team will not get his data, especially of the race-simulation runs, which could harm their chances of setting up the car in the optimum fashion for the race.
The first session was effectively a write-off on a soaking track as only 11 drivers even set a time. Toro Rosso's Daniel Ricciardo was fastest from Sauber's Nico Hulkenberg.
British Grand Prix Grand Prix, day two
- Saturday, 29 June:
- Third practice: BBC Two & Radio 5 live sports extra 09:55 BST, live text and audio commentary on the BBC Sport website. Qualifying: BBC One 12:15 BST & 12:55 BST Radio 5 live sports extra, live text commentary on the BBC Sport website
British Grand Prix Grand Prix, day three
- Sunday, 30 June:
- Race: Coverage on BBC One 12:10 BST, BBC Red Button 12:00 BST & Radio 5 live from 13:00 BST; live text commentary on the BBC Sport website. F1 Forum 15:30 BST. TV highlights 19:00 BST, BBC Three