Ferrari gave a firm hint that its upgrade package has vaulted it back into contention by taking a comfortable one-two in the final practice session at Barcelona.
Felipe Massa topped the session by 0.082 seconds over team-mate Kimi Raikkonen, with championship leader Jenson Button third for Brawn, nearly half a second down on Raikkonen's time.
Rubens Barrichello was right behind his team-mate in the second Brawn, with Robert Kubica completing the top five for BMW.
The Ferraris led the way for much of the hour, with Massa and Raikkonen usurping early pace-setter Fernando Alonso (Renault) to hold a one-two by the halfway point.
Barrichello put Brawn to the front after 41 minutes, albeit only briefly before Massa retook the position for Ferrari.
At that stage all the frontrunners were still on hard tyres, but in the final 14 minutes the qualifying-style runs began in earnest, with Toyota's Timo Glock the first to bolt on a set of softs and jump to the front 14 minutes from the end.
His 1m21.377s was totally eclipsed when Massa tried softs, though, as the 2007 race winner produced a 1m20.553s on his final run.
Even the Brawns could not match that, and Raikkonen then emphasised Ferrari's pace by returning to second place - initially 0.3s behind Massa before closing the gap to less than a tenth of a second.
Behind the Ferraris, Brawns and Kubica, Toyota duo Jarno Trulli and Glock were sixth and eighth, split by Lewis Hamilton's McLaren.
Sebastien Buemi put the revised Toro Rosso in the top ten again in ninth ahead of local hero Alonso.
Friday afternoon pace-setter Nico Rosberg was only 12th, having had a brief trip off the road at Campsa in his Williams.
It was a low-key session for Red Bull too, with Mark Webber and Sebastian Vettel back in 13th and 16th positions.
Nick Heidfeld sat out the second half of the session after crashing his BMW at Turn 12. The left front corner was heavily damaged, leaving Heidfeld at the bottom of the times once everyone else had switched to qualifying simulations.
Force India's Giancarlo Fisichella had a less dramatic incident, spinning out of Turn 7 but rejoining unscathed after a visit to the grass.
Pos Driver Team Time Laps 1. Massa Ferrari (B) 1:20.553 18 2. Raikkonen Ferrari (B) 1:20.635 + 0.082 22 3. Button Brawn-Mercedes (B) 1:21.050 + 0.497 19 4. Barrichello Brawn-Mercedes (B) 1:21.163 + 0.610 17 5. Kubica BMW Sauber (B) 1:21.239 + 0.686 21 6. Trulli Toyota (B) 1:21.256 + 0.703 23 7. Hamilton McLaren-Mercedes (B) 1:21.346 + 0.793 16 8. Glock Toyota (B) 1:21.377 + 0.824 26 9. Buemi Toro Rosso-Ferrari (B) 1:21.424 + 0.871 19 10. Alonso Renault (B) 1:21.499 + 0.946 17 11. Kovalainen McLaren-Mercedes (B) 1:21.519 + 0.966 15 12. Rosberg Williams-Toyota (B) 1:21.594 + 1.041 20 13. Webber Red Bull-Renault (B) 1:21.629 + 1.076 19 14. Bourdais Toro Rosso-Ferrari (B) 1:21.649 + 1.096 19 15. Piquet Renault (B) 1:21.685 + 1.132 18 16. Vettel Red Bull-Renault (B) 1:21.689 + 1.136 18 17. Fisichella Force India-Mercedes (B) 1:21.909 + 1.356 19 18. Nakajima Williams-Toyota (B) 1:22.043 + 1.490 19 19. Sutil Force India-Mercedes (B) 1:22.232 + 1.679 19 20. Heidfeld BMW Sauber (B) 1:23.457 + 2.904 8