Valtteri Bottas completed his first full-race simulation on board a Mercedes on Tuesday as the defending constructors' champions enjoyed another fruitful day in Barcelona.
Bottas' team-mate Lewis Hamilton completed 66 laps in the first session of the day and was comfortably quickest, nearly two seconds clear of nearest rival Kimi Raikkonen.
The Briton handed over the W08 to Bottas after lunch and the Finn was able to get valuable track time in his new car, even if he was well down on time.
Bottas completed 102 laps but could only manage the seventh quickest time, which was over two seconds slower than Hamilton had achieved earlier in the day.
And it was not all plain sailing for the Mercedes newcomer as he had a brief flirtation with the wall following a spin.
Hamilton was denied a second successive day on top, though, as Raikkonen found more pace in his Ferrari and usurped his rival by two hundredths with a lap time of 1:20.960 seconds.
The technical issues that dogged Daniel Ricciardo on day one were nowhere to be seen as Max Verstappen took the Red Bull RB13 onto the track, the Dutchman able to rack up 89 laps and be the closest contender to Raikkonen and Hamilton.
Haas enjoyed a strong showing from Kevin Magnussen as he completed more laps than any other driver, while Esteban Ocon made his first Force India outing.
It was not so profitable for Lance Stroll after a crash early in the day ended Williams' participation, with Renault and McLaren both being stifled by reliability issues.