Valtteri Bottas ensured that Mercedes finished on top of the time sheets after the second day of in-season testing at the Circuit de Barcelona-Catalunya.
The Finn set a time of 1:16.904s in the W09 on the supersoft compound just before lunch. It compared to Lewis Hamilton's Spanish Grand Prix pole time of 1:16.173s at the weekend.
Bottas was over half a second up on the fastest time set on Tuesday by Red Bull's Max Verstappen. Having completed 60 laps in the morning, he added another 79 after the break for a total of 139 laps of the 16-turn, 4.655km (2.892 mile) venue on Wednesday.
A quiet afternoon meant that Ferrari's Antonio Giovinazzi retained second at the chequered flag, a slender 0.068s behind Bottas albeit on the hypersoft tyres. He completed more runs than anyone else on the day, with 148 laps in the books.
Lando Norris moved into third place on the timing screens in the final minute of the session. His time of 1:18.039s was completed on a set of soft tyres.
Norris had spun at turn 12 in the morning session, blaming the wind that had been such a feature of last weekend's race. "It's the one corner that has been quite tricky because of the wind," he said. "It was more of a mistake on my part, I pushed the entry a bit too much and lost the rear."
Norris also triggered a red flag in the afternoon when the MCL33 came to an inconvenient halt with a "minor issue" on an out lap, but the car was quickly resuscitated and back out.
Kevin Magnussen ended the day fourth fastest for Haas. Like Giovinazzi, he set his best time on a set of hypersofts. However, Magnussen was also the cause of the first red flag of Wednesday's afternoon session when he stopped on track between turns 2 and 3.
The Dane's day was done after a total of 75 laps, with the team reporting that it was ending its test day early to investigate the cause of the VF-18's stoppage.
Force India's Nikita Mazepin was fifth fastest, setting his best lap 20 minutes from the end on a set of soft tyres. Jack Aitkin's first test for Renault saw him finish sixth, his time on ultras having been set before lunch.
Sauber's Charles Leclerc and Williams' test and development driver Robert Kubica also found no improvement in their morning pace after the mid-day break.
At Toro Rosso, Pierre Gasly took over in the afternoon from Sean Gelael. He was ninth fastest on his limited outing of 39 laps, just ahead of Stoffel Vandoorne who was running tests for Pirelli in a second McLaren car.
Red Bull's debutant Jake Dennis improved on his morning but was still only tenth fastest ahead of Gelael and the second Pirelli test car driven by Force India's Nicholas Latifi who was the slowest of the 13 drivers taking part.
Barcelona in-season test - Day 2 final times
|4||Magnussen||Haas F1||1:18.274 (+1.370)||75|
|5||Mazepin||Force India||1:18.344 (+1.440)||112|
|9||Gasly||Toro Rosso||1:19.410 (+2.506)||39|
|11||Dennis||Red Bull Racing||1:20.440 (+3.536)||74|
|12||Gelael||Toro Rosso||1:20.763 (+3.859)||83|
|13||Latifi||Force India||1:21.433 (+4.529)||121|