Valtteri Bottas looked happy after his first outing in the new Mercedes-AMG F1 W08 Power+ at the Circuit de Barcelona-Catalunya.
Bottas completed 79 laps in the car on Monday morning on the first of four days of pre-season testing taking place this week in Spain.
"It was very good for the first morning," said Bottas, who moved from Williams to join the team over the winter after the shock retirement of world champion Nico Rosberg at the end of 2016.
"Very different to last year, I have to say," he added. "Definitely feel with the new regulations the increased loads and bigger car, more grip."
"Obviously it's a completely different car anyway, different from the Williams - behaving slightly differently. But it's still a car with four wheels, and an engine and a steering wheel.
"Everything was running very smoothly. First time on track today with the car, it’s a very good start.
"We had zero problems on the engine side or with the car mechanically or aerodynamically, so everything was running smoothly, checking the systems.
"The feeling was nice, good to feel the extra downforce. I’ve never driven a car with that much downforce, that’s for sure."
After setting a best lap time of 1:23.169s in the morning, Bottas handed over the car to his team mate Lewis Hamilton for the afternoon stint.
The situation is reversed on Tuesday, with Hamilton due to run in the morning and Bottas back in the car again, this time for the afternoon stint.
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