Pascal Wehrlein kept Mercedes at the top of the times on the final morning of the Barcelona in-season test as Jenson Button delivered a step forward for McLaren.
While Nico Rosberg had been more than two seconds clear of the field on Tuesday, Wehrlein's best time of 1:26.641 left him with an advantage of 0.798s. Wherlein had a busy morning despite not having fully recovered from the illness which forced him to pull out of a day driving for Force India, completing 73 laps in a session interrupted by a crash for Raffaele Marciello.
Driving for Sauber after being in the Ferrari on Tuesday, Marciello went off at Turn 3 after eight laps, on a lap when he was analysing different settings in different corners. The front left corner of the car was damaged, and despite Sauber being hopeful of a return to the track within an hour, Marciello failed to emerge again before lunch.
Jolyon Palmer was second quickest for Lotus thanks to a lap on soft tyres late in the morning session, posting a 1:27.439 as he completed 40 laps in the E23, following on from his FP1 run in Barcelona.
Button was back in the McLaren MP4-30 for the first time since describing it as "scary to drive" during Sunday's Spanish Grand Prix. The 2009 world champion was much happier with the handling of the car on Wednesday morning and duly set the third fastest time despite running on high fuel, just 0.047s slower than Palmer.
Ferrari gave Esteban Gutierrez his first taste of the SF15-T and he ended the session fourth fastest, half a second slower than Button. Gutierrez completed 66 laps on his first morning in the car, and was just 0.008s quicker than Carlos Sainz in the Toro Rosso.
There was limited mileage for Alex Lynn, who completed 19 laps driving the Williams for the first time. Lynn's best time was within two seconds of Wehrlein, but he will hope to get more laps under his belt in the afternoon session.
Esteban Ocon managed 45 laps in the Force India having only been called up to drive on Tuesday morning, with the GP3 championship leader three seconds off the pace. Fellow Frenchman Pierre Gasly failed to set a time despite 22 laps for Red Bull in the morning session.
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