Sebastian Vettel was fastest again on day two of the Barcelona test, as Red Bull went for shorter runs for the first time and gave a hint of its potential.
The world champion went for a string of qualifying-style one and two-lap runs late in the morning, during which he quickly went to the top of the times, and then repeatedly improved his pace until he reached the 1m23.315s that stood as the day's best.
In a very productive day for Red Bull, the team also got through a large number of pitstop simulations, though its attempt to get through a race distance in the afternoon was interrupted by first a red flag, then a problem with Vettel's car that caused a long pause in the garage.
Toro Rosso's good form continued as Jaime Alguersuari took second place. After some short runs in the 1m24s/1m25s region in the morning and then a longer stint through the middle of the day, the Spaniard's best time came on the first lap of a three-lap stint late on. He ended up 0.2 seconds slower than Vettel.
Ferrari's so-far excellent reliability took a slight downturn today, with an electrical problem stranding Fernando Alonso on an out-lap this morning. That was quickly rectified, but further mechanical problems kept Alonso in the garage for a while in the middle of the day.
Once repaired, the Ferrari was fast again, doing some very respectable long runs and then jumping to third with a 1m23.978s in the final half hour.
Another man to improve in the closing stages was Williams's Rubens Barrichello. He produced a string of low-1m24s at the start of 10-lap runs, and with 116 trouble-free laps completed, this was the team's best day of the winter so far in reliability terms.
Renault split the day between Nick Heidfeld and Vitaly Petrov as the latter had lost a lot of running to KERS issues yesterday. Petrov was 11th after 61 laps this morning, while Heidfeld did just 41 laps but made a late move into fifth place.
Sauber started the day with long runs for Kamui Kobayashi, before a five-lap stint this afternoon saw him set the 1m24.243s that would give him sixth place.
Nico Rosberg was seventh. He also started the day with some lengthy stints, as Mercedes showed better consistency over a run than of late, though it still appeared slightly lacking in outright pace compared to its main rivals. His best time of the day was on a qualifying-style one-lap dash.
McLaren had a troubled start to the day as hydraulic problems kept Jenson Button off-track for most of the morning. He only managed 54 laps during the day as he took eighth.
Paul di Resta was competitive in the morning with Force India but lost some afternoon running after going off at Turn 1 due to a throttle problem. He was ninth ahead of Lotus's Heikki Kovalainen, who lost a bit of time to a few mechanical issues during the day.
Lotus also gave Portuguese-Angolan driver Ricardo Teixeira 26 laps as the Formula 2 graduate pushes for a test position. He was 8.3s off the pace and slowest.
Another new sight today was Tonio Liuzzi in the Hispania. He had 70 laps to get used to the car and was 3.7s off the pace in 12th, ahead of Timo Glock. Virgin spent the whole morning during systems and aero checks, before picking up pace this afternoon once new parts had arrived.
Pos Driver Team Time Laps 1. Vettel Red Bull-Renault 1m23.315s 104 2. Alguersuari Toro Rosso-Ferrari 1m23.519s + 0.204 97 3. Alonso Ferrari 1m23.978s + 0.663 90 4. Barrichello Williams-Cosworth 1m24.008s + 0.693 118 5. Heidfeld Renault 1m24.242s + 0.927 41 6. Kobayashi Sauber-Ferrari 1m24.243s + 0.928 125 7. Rosberg Mercedes 1m24.730s + 1.415 131 8. Button McLaren-Mercedes 1m24.923s + 1.608 54 9. Di Resta Force India-Mercedes 1m25.194s + 1.879 80 10. Kovalainen Lotus-Renault 1m26.421s + 3.106 58 11. Petrov Renault 1m26.884s + 3.569 61 12. Liuzzi HRT-Coswrorth 1m27.044s + 3.729 70 13. Glock Virgin-Cosworth 1m27.242s + 3.927 66 14. Teixeira Lotus-Renault 1m31.584s + 8.269 26 All Timing Unofficial