Sergio Perez put McLaren on top on day two of Barcelona Formula 1 testing.
The Wednesday afternoon session featured few changes from the opening part of the day, but the most significant came early on.
Perez's lap of 1m21.848s was achieved on a one-lap sprint on soft tyres, and deposed morning pacesetter Sebastian Vettel by 0.349 seconds.
Red Bull attempted a race simulation in the afternoon, albeit one punctuated by lengthy sessions in the garage.
Vettel then came to a halt just past on the pit exit when he rejoined after his third pitstop of the run because of a loose wheel.
But the Red Bull was swiftly revived in the garage and able to rejoin for the final minutes of the session.
Vettel's issue caused one of only two red flags all day, the second coming when Max Chilton parked his Marussia on track in the closing minutes.
After losing the entire morning while his Lotus underwent a gearbox change, Kimi Raikkonen managed 43 laps in the afternoon.
He jumped to third quickest with his first outing and remained there, half a second behind Perez.
Lewis Hamilton and Fernando Alonso completed the top five, followed by Valtteri Bottas on his debut in the new Williams FW35.
Hamilton completed the most laps of the day with 121.
Pos Driver Team Time Gap Laps Tyre
1. Sergio Perez McLaren 1m21.848s 97 Soft
2. Sebastian Vettel Red Bull 1m22.197s +0.349 84 Soft
3. Kimi Raikkonen Lotus 1m22.697s +0.849 43 Medium
4. Lewis Hamilton Mercedes 1m22.726s +0.878 121 Hard
5. Fernando Alonso Ferrari 1m23.247s +1.399 76 Medium
6. Valtteri Bottas Williams 1m23.561s +1.713 98 Soft
7. Daniel Ricciardo Toro Rosso 1m23.718s +1.870 70 Medium
8. Paul di Resta Force India 1m23.971s +2.123 62 Medium
9. Nico Hulkenberg Sauber 1m24.205s +2.357 88 Medium
10. Max Chilton Marussia 1m25.115s +3.267 67 Soft
11. Charles Pic Caterham 1m26.243s +4.395 102 Medium