Vettel tops opening day at Barcelona

On what may have been the hardest-to-read session of the winter so far, it took until lunchtime for the track to fully dry following Thursday's heavy rain.

That meant the majority of drivers' fastest times were set during short exploratory runs late in the morning just as the circuit was at the tipping point of being ready for slick tyres, before teams switched to longer runs in the afternoon.

Alonso's 1m25.485s in the Ferrari during this period looked set to stand as the day's best, as the Spaniard switched to mid-range stints in the afternoon, covering between eight and 17 laps at a time, with a pace generally starting in 1m27s then fading to 1m29s by the end of his run.

Vettel completed relatively little running until the closing stages of the day, when he started a pair of short runs, lapping mostly in the 1m26s during the first outing before re-emerging from the pits to blast in a 1m24.374s with nine minutes to go.

That pace deposed Alonso by a full second, although it seemed Red Bull might have been using super soft tyres, as Vettel's times dropped off by 1-2s for the remainder of his seven-lap run.

Toro Rosso's Jaime Alguersuari and Sauber's Kamui Kobayashi again set good times during relatively short runs to put themselves third and fourth. Both also caused red flags during the day - the Sauber running dry during a fuel consumption evaluation, and Alguersuari going into the Turn 4 gravel.

McLaren had another fairly quiet day, with Jenson Button sitting out much of the afternoon and taking fifth.

Paul di Resta was not able to get the Force India on track until the final few hours while the team waited for new parts for the VJM04. When he did though the Scot was able to swiftly move up to sixth despite only managing 24 laps all day.

There were more glitches at Williams, where Rubens Barrichello - the first to get good pace out of slicks in the morning - caused a red flag just before the lunch break and then was sidelined for nearly the whole afternoon while the team made a precautionary engine change. That left him seventh.

Eighth-placed Michael Schumacher spent his afternoon doing a race simulation in the Mercedes, covering a full grand prix distance broken up by quick pitstops. His pace tended to start in the 1m29s/1m30s region before going up by 2-3s over the course of his 13-15 lap stints.

His final total for the day was 89 laps, beaten only by Narain Karthikeyan in the 2010 Hispania (114 laps) and Jerome D'Ambrosio's Virgin (115). The latter pair were ninth and 11th, split by Lotus driver Heikki Kovalainen, who lost some track time with a water leak.

It was a difficult day for Renault. Its intention had been to let Vitaly Petrov have most of the session after Nick Heidfeld had completed some pitstop practice, but after the German's early appearance, Petrov had to wait until late afternoon before he could join in, as a KERS software glitch kept the car in the garage.

Pos  Driver              Car/team              Time       Gap        Laps
 1.  Sebastian Vettel    Red Bull-Renault      1m24.374s             37
 2.  Fernando Alonso     Ferrari               1m25.485s  + 1.111s   101
 3.  Jaime Alguersuari   Toro Rosso-Ferrari    1m25.638s  + 1.264s   57
 4.  Kamui Kobayashi     Sauber-Ferrari        1m25.641s  + 1.267s   78
 5.  Jenson Button       McLaren-Mercedes      1m26.365s  + 1.991s   77
 6.  Paul di Resta       Force India-Mercedes  1m26.575s  + 2.201s   26
 7.  Rubens Barrichello  Williams-Cosworth     1m26.912s  + 2.538s   52
 8.  Michael Schumacher  Mercedes              1m27.512s  + 3.138s   90
 9.  Narain Karthikeyan  HRT-Cosworth          1m28.393s  + 4.019s   116
10.  Heikki Kovalainen   Lotus-Renault         1m30.065s  + 5.691s   54
11.  Jerome D'Ambrosio   Virgin-Cosworth       1m30.950s  + 6.576s   116
12.  Vitaly Petrov       Renault               1m35.174s  + 10.800s  20
13.  Nick Heidfeld       Renault               1m44.324s  + 19.950s  27

All timing unofficial