Ferrari's Formula One leader Charles Leclerc was fastest in Spanish Grand Prix practice on Friday with George Russell and seven times world champion Lewis Hamilton second and third for Mercedes.
Ferrari introduced upgrades to try to close the performance gap to rivals Red Bull, who have won the last two races with world champion Max Verstappen, and they seemed to be working well.
Leclerc set a best time of one minute 19.670 seconds on the faster soft tyres in the late afternoon sunshine with Russell 0.117 slower, also on the soft compound, and Hamilton 0.204 off the pace.
Reigning champions Mercedes, struggling to tame a bouncing car in the first five races of the season, seemed to be making progress with their "porpoising" problem.
"The car is definitely reacting differently and we have different limitations this time," said Russell.
"We definitely don't have the porpoising in the straight but we are experiencing a bit here and there in the corners," added the Briton.
Red Bull team boss Christian Horner said Mercedes appeared to be getting on top of their issues.
"They've had a strong day today, by the looks of things, so we've got a few bits we need to tidy up," he told Sky Sports television.
Leclerc lapped in 1:19.828 in the first session, with Spanish team mate Carlos Sainz 0.079 slower and Verstappen third. Sainz was fourth in session two with the Dutch driver fifth.
Leclerc has a 19-point advantage over Verstappen while Ferrari have seen their lead whittled back to six in the constructors' standings.
"It's been close since the beginning of the season and every time they (Red Bull) have brought upgrades they have been closer and closer and now I think are a bit in front, especially in terms of race pace," Leclerc told reporters earlier.
"I hope it (the upgrades) will be enough for us to jump back in front."
Verstappen has won three races this season and Leclerc the other two.
Russell was fourth in the first session and Hamilton sixth.
Alpine's two times world champion Fernando Alonso was fifth and sixth respectively in the sessions.
Formula E champion and Mercedes reserve Nyck de Vries made his grand prix weekend debut in place of Thai driver Alex Albon at Williams for the opening session and was 18th but quicker than Canadian regular Nicholas Latifi.
Estonian Juri Vips replaced Sergio Perez in the Red Bull, and was last while experienced Polish reserve Robert Kubica took the wheel of Guanyu Zhou's Alfa Romeo and put in the 13th fastest lap.
Valtteri Bottas stopped his Alfa Romeo on track early in the second session and McLaren's Lando Norris damaged the floor of his car after only six laps and sat out the remainder of the afternoon.