Mercedes trackside engineering director Andrew Shovlin believes the Silver Arrows made made "good progress" on the first day of pre-season testing in Spain.
George Russell completed 77 laps in the morning to complete his first official duties as Lewis Hamilton's team-mate, before the seven-time champion added 50 laps of his own in the afternoon.
It was not the first time the W13 had hit the track, although the stormy conditions at Silverstone last week meant the team had no representative running to begin the day with at the Circuit de Barcelona-Catalunya.
"We got through a lot of work today and both drivers have been able to give us their initial impressions of the W13," explained Shovlin.
"Overall the day has been surprisingly straightforward although looking up and down the pitlane, you can see how high the reliability standards are and most teams seemed to be running their programmes without issue.
"There really is a lot to try and cram into the six days of winter testing when you consider how different the car and the regulations are.
"Nevertheless, we have made good progress on understanding the aerodynamics and the tyres, while at the same time getting nearly 600km under our belts.
"From a pace point of view it's too early to say where anyone stands, we've also got a few wrinkles to iron out in terms of balance and performance before really trying to put times on the board.
"However, our overall feeling from today is a good one and we're looking forward to making more progress tomorrow."