Nico Rosberg set the pace in Saturday's final practice for the Spanish GP while team-mate Lewis Hamilton refused to show his hand.
On another warm morning in Spain, McLaren's Danish driver Kevin Magnussen got proceedings underway with a 1:28.771 as Sebastian Vettel, in need of making up time after completing just four laps on Friday with an electrical problem, was also quickly into the action, going second quickest.
Kimi Raikkonen had a turn at the front as did Fernando Alonso, however, when the Mercedes duo came out for their first runs they immediately claimed the 1-2.
Nico Rosberg went quickest by a full second over Alonso only to lose out to Lewis Hamilton by 0.3s. The German jumped ahead again by two-tenths while Hamilton backed off, leaving everyone wondering what he really could do.
While Jenson Button and Nico Hulkenberg both complained about their rear tyres overheating, Vettel was the first to swap to the medium tyres. The German improved to third but was still 1.5s down on Rosberg's best on the hard Pirelli tyres.
The Mercedes duo swapped over with 15 minutes to go with Rosberg extending his lead by 0.7s over his hard tyre run. Hamilton, despite being on par with his team-mate through the second sector, peeled off into the pits instead of completing his lap.
The British driver climbed out of his car, declaring his morning's work done without showing his hand while Rosberg did a few out-and-in laps as he practiced starts in the pit lane.
But while the Mercedes drivers were having a good morning the same cannot be said of Max Chilton. Making a mistake at Turn 5 the Marussia driver found himself beached in the gravel with 10 minutes still remaining.
Back in the action, Alonso climbed to third place but was still 1.301s down on Rosberg's best. Felipe Massa finished fourth ahead of the much improved Lotus of Romain Grosjean and Magnussen.
01 Nico Rosberg Mercedes 1:25.887 16 laps
02 Lewis Hamilton Mercedes 1:26.756 +0.869 9 laps
03 Fernando Alonso Ferrari 1:27.188 +1.301 15 laps
04 Felipe Massa Williams 1:27.223 +1.336 10 laps
05 Romain Grosjean Lotus 1:27.682 +1.795 18 laps
06 Kevin Magnussen McLaren 1:27.806 +1.919 16 laps
07 Daniel Ricciardo Red Bull 1:27.808 +1.921 12 laps
08 Jenson Button McLaren 1:28.006 +2.119 11 laps
09 Pastor Maldonado Lotus 1:28.076 +2.189 19 laps
10 Sebastian Vettel Red Bull 1:28.085 +2.198 20 laps
11 Valtteri Bottas Williams 1:28.101 +2.214 12 laps
12 Jean-Eric Vergne Toro Rosso 1:28.242 +2.355 16 laps
13 Daniil Kvyat Toro Rosso 1:28.298 +2.411 16 laps
14 Kimi Raikkonen Ferrari 1:28.419 +2.532 16 laps
15 Sergio Perez Force India 1:28.571 +2.684 13 laps
16 Nico Hulkenberg Force India 1:28.668 +2.781 13 laps
17 Adrian Sutil Sauber 1:28.715 +2.828 16 laps
18 Esteban Gutierrez Sauber 1:28.865 +2.978 18 laps
19 Max Chilton Marussia 1:30.169 +4.282 15 laps
20 Jules Bianchi Marussia 1:30.670 +4.783 12 laps
21 Kamui Kobayashi Caterham 1:30.712 +4.825 18 laps
22 Marcus Ericsson Caterham 1:31.559 +5.672 19 laps