During his busy morning behind the wheel, he completed 58 laps and put in a best time of 1:20.349 (on the Medium tyre) just before lunchtime to go second fastest.
"Our first morning here in Barcelona was very positive," said the Finn, after climbing out of the car. "We got everything done that we had planned. The main mission for the morning was to gather aerodynamic data, so I was doing runs at constant speeds.
"I got a few practice laps for myself as well; but that kind of running was very limited. We didn't do any performance running, so I haven't pushed the W09 to its limits yet. The initial feeling of the car was good, it was behaving well. I couldn't point out any negatives compared to last year's car, only positives so far.
"It was really good to be back in the car; it felt like I haven't been away at all. It didn't take any time to get used to the car - that's a good feeling. Driving these cars is still hard work for the drivers, but I had a good training programme over the winter, so I felt physically prepared.
"The weather conditions today were a bit tricky with the cold temperatures. Neither the cars nor the tyres are made to be driven in five degrees Celsius. That's been the main challenge of the day, but that's the same for everyone. The amount of testing we can do is limited so we have to make the most of it."