Nikita Mazepin made an impressive debut for Mercedes today, the young Russian completing the most laps and topping the timesheets.
With Valtteri Bottas topping the times yesterday, this means that Mercedes has achieved yet another 1-2, while leaving Ferrari over 0.7s in its wake.
A day which saw 13 drivers on duty, two of them for Pirelli, was punctuated by a number of red flags stoppages, with Mazepin and Latifi stopping on track this morning and Sergio Sette Camara and Alexander Albon this afternoon, all three choosing to park up at Turn 10.
It was 20-year-old Mazepin's first day of testing for Mercedes, and few will have failed to be impressed by his pace and consistency as the German team continued with aero data collection and power unit work. The Russian completed a long run programme in the morning before moving to single lap runs in the afternoon, thereby allowing him to gain experience on the three softest tyre compounds.
"Today was incredible," he admitted. "Being a part of this team, even just for this day was very special for me. It's every young driver's dream to drive a car like this and today mine came true, so I'm really happy.
"Importantly it was a successful day on track too, we gathered most of the data we set out to collect, we didn't encounter any problems and from my side I felt I could deliver consistently throughout the day - which is important for the team. In the afternoon we were competitive on the performance runs and the car felt great. Everyone in the team is working so hard and you can feel that when you sit in this car."
"It's been another successful day, and we managed to complete all of the programme we had planned," added Sporting Director, Ron Meadows. "We spent the first three quarters of the day focused on aerodynamic and power unit development testing, before switching to one-lap performance runs, working through the different specifications of the tyre with Nikita.
"He did a really superb job today, just as we expected he would," he concluded.
"I think it was a very productive day," said Alexander Albon, who finished second quickest, albeit 1.3s off Mazepin's pace, having completed 109 laps, "as we completed all the runs we had planned.
"We learned more about the updates we brought here for the weekend and how they were working," he added, "I'm sure we will be able to take a lot of the things we learned from the test to the next races.
"On my side, I'm understanding more how I want the car to be and where I want the setup for qualifying. All in all, we got a lot done today."
"Alex took over from Daniil and completed some very important aero data gathering that kept us busy for most of the morning session," said Guillaume Dezoteux, the team's head of vehicle performance. "Before lunch, despite the two red flags, we managed to perform a couple of short runs on the C3 tyre compound for further tyre optimization.
"The wind picked up in the afternoon which made the car more inconsistent and difficult to drive for Alex. We focused on suspension setup to explore different approaches on the C2 rubber which was working well for him during the race. We followed this sequence by a couple of test items on the C3 compound and finally moved to the C4 to conclude on performance runs.
"We can be very happy how the in-season tests went for us. Both cars and the PU ran reliably, the drivers didn't make any mistakes and the team has been able to bring home a huge amount of data to analyse.
"Obviously, it is a challenge to stop testing that early in the season with 16 races still to go, but we are looking forward and we will do our best to improve our package from the data gathered here."
"We had another useful day of testing, following a similar programme to yesterday," said Masamitsu Motohashi, Honda F1 Deputy Technical Director. "That means we worked on some items aimed at long term development, while also looking at PU settings that we might run in Monaco, where practice starts in a week's time.
"Our PU worked smoothly over the two days and we completed a total of 231 laps with Scuderia Toro Rosso. Monaco GP is next on our agenda, so we'll be analysing all the data we gathered here to make further improvements for this event."
Ferrari added a further 247 laps to its total, Antonio Fuoco working for the team and Charles Leclerc carrying out tyre development work for Pirelli.
In the first four hours, Leclerc did 73 laps at the wheel of his SF90, with a best time of 1:18.666, while Fuoco did 66. The Italian did not push too hard on the opening laps, as he got to grips with the car, having covered a very high mileage in the simulator.
It was Fuoco's first drive in a current machine, as his last test dated back to 2016, when the technical specification of the cars was quite different. He ran both the C2 and C3 tyres, while trying some specific components in a series of short runs, to continue the car's development programme, which allowed him to make a first hand comparison with driving in the simulator. His best time was a 1:18.182.
After the lunch break, Leclerc continued the development work for Pirelli, some of it already looking at 2021, while Fuoco concentrated on some long runs, which helped him get a good understanding of the SF90.
Leclerc covered a total of 127 laps, with a best time of 1:17.349, while Fuoco did 120 laps and also tried the C4 compound tyres. His best lap was a 1:17.284.
"It was a positive day," said Fuoco. "We completed various tests and ran a total of 120 laps. In terms of the programme, we concentrated on short runs with different tyre compounds in the morning followed by longer runs in the afternoon and performance runs at the end of the day. The car felt really good to drive.
"It will be important for us to analyse the data we collected today, as well as the correlation with the simulator, given that I do a lot of work in it. I really enjoyed the day and would like to thank the team for this opportunity."
"It was a pretty good day in the car," said Kimi Raikkonen, who completed 110 laps on his way to posting the fifth best time of the day. "After yesterday's issues we had to change our testing programme slightly but we managed to go through all the different things we wanted to try.
"We had the chance to work with different compounds, we worked on the set-up and we put a few different parts on the car, so it was a busy day. I feel that if we did the race weekend again, we'd be stronger than we were."
Haas wrapped up its test with Kevin Magnussen, at the wheel, the Dane building on the 103-lap tally set by test driver Pietro Fittipaldi on Tuesday.
Magnussen clocked 46 laps by the mandatory lunch hour, the Dane ending the morning session fastest overall with a best time of 1:18.101, set on the C3 tyre.
An extensive afternoon run plan added a further 60 laps as Magnussen circulated exclusively on the C3 rubber. His pre-lunch hot lap remained his fastest placing him seventh overall.
"I was happy to get a lot of laps on a test like this straight after a race weekend," said the Dane. "It's really useful to be able to evaluate everything back-to-back.
"We've tried some interesting stuff and gathered a lot of data to go through. We're not chasing a lap time, we're giving specific feedback, gathering data.
"Some things were good, some not so, but it's testing, so we're trying stuff that's not necessarily going to make you faster - you're just getting information to help you make progress. Overall though, it's been a productive test day. I'm happy."
Racing Point completed its second day of running with Nick Yelloly once again on track in the RP19, while Lance Stroll was behind the wheel of a second car to support the Pirelli testing programme.
"Conditions have been a bit more challenging today," admitted Brad Joyce, the team's head of trackside performance, "with higher winds creating a dusty circuit and making things a little less straightforward. Turns three, nine and twelve in particular have been very tricky.
"Nonetheless, it's been a useful session. Lance has driven the Pirelli car today and completed the full programme for them. With Nick in the test car, we focused on long-term aero development and correlation work. He's done a good job - driving well, giving accurate feedback and not putting a foot wrong.
"Monaco is a very different circuit to Barcelona, but we've gathered a lot of data during this test which will be useful next week and for the races beyond."
Check out our Wednesday gallery from Barcelona, here.