He set the fastest time in the afternoon testing session in Barcelona
Britain's Lewis Hamilton has enjoyed a successful return to Formula One on the first day of testing ahead of the new season.
He went one better than new Mercedes team-mate Valtteri Bottas in setting the fastest time in the afternoon session in Barcelona.
"It has been a good day, a positive day for the team," Hamilton told the BBC. "Lots of laps and information gained so we can try to improve the car.
"I was always trying to pick up the speed through the corners and you have to drive a little bit different. It is a beast. It is so much better than last year."
He added: "Normally you have a lot of degradation in these tyres but these ones don't. But there is not a lot of performance at the beginning of the tyre.
"They are very consistent, hard tyres. There is not a big difference from early on to later. There is a bit of a drop-off but not massive."
Ferrari's Sebastian Vettel was second quickest - after finishing ahead of Bottas this morning.
It wasn't such a productive day for McLaren and Red Bull - who suffered with engine and gearbox problems respectively.