The first week of testing saw a very strong start for Mercedes, as they introduced the ‘Dual-Axis Steering’ system and Valtteri Bottas set the fastest time of 1:15.732.
But with a focus very much on learning and understanding Hamilton finished the day in P7 on 89 laps and a time of 1:17.562.
“It's been a good session and a good start to the second week of testing here in Barcelona,” he said.
“We've just got our heads down, trying to continue increasing our mileage and our understanding of this car - through the subtle changes with car set-up, the tyres and the aerodynamic package.”
Conditions were a difficult factor for some teams throughout the day, most notably Max Verstappen’s spin in his Red Bull towards the end of the afternoon session.
Hamilton felt a difference from the wind, as well as having less grip on the track than usual.
“A fairly standard day, but it was a bit windier out there and it felt like the track had less grip - so there was some sliding around,” he added.
“The car didn't quite feel as good as the first week, but I'm sure that will change as the test progresses and the track conditions improve.”
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