With McLaren and Force India both running two cars - one on behalf of Pirelli as it continues its testing of its 2019 compounds - there were 13 drivers on duty again today.
Between them they completed 1,350 laps, just 88 laps less than yesterday.
At Mercedes, one of the main priorities in the morning session was completing a series of aerodynamic test items, before the focus switched to shorter runs. In the afternoon, Valtteri Bottas moved onto longer runs. His best time of 1:16.904 was set on the supersoft shortly before the lunch break.
"Today was really interesting," said the Finn, "and we got through our programme fairly smoothly. We had a good baseline from last weekend and used it to work on different set-ups, trying out bigger changes than we normally would on a race weekend.
"We also tried to gather some information on the tyres, as we will see similarly smooth tarmac at Silverstone and Paul Ricard. I enjoyed being back in the car today, I'm looking forward to being back in action next week in Monaco.
"We've had another very useful day of testing," added Andrew Shovlin, "with the car running faultlessly throughout. We had a fairly similar programme to Lewis, using the early part of the day to do a number of the aerodynamic test items, then getting into a programme of short run work before lunch and longer runs in the afternoon.
"There were a few cars that stopped on track in the afternoon causing red flags, which does impact on your plans. But, we have been able to complete almost all the important work we had planned and have made some good progress in further understanding the car and tyres. We have a very busy few days coming up, finishing our analysis from the race and test and getting stuck into preparations for Monaco to ensure we are ready for its unique challenges."
Antonio Giovinazzi, despite feeling a bit under the weather, was on duty for Ferrari, the Italian having driven the Sauber yesterday.
The Italian completed 148 laps, posting the second best time of the day on the hypersoft tyres.
"It was a tiring day," he said. "We did a lot of laps, but I really enjoyed it. Apart from yesterday, driving the Alfa Sauber, I hadn't driven in an official test session since last year in Abu Dhabi. We had an interesting programme to work on, with various things to test and different tyre compounds to try.
"The test was productive and delivered a really big amount of data to correlate with that from the simulator. To be at the wheel of a Ferrari is always a privilege and it was a fantastic feeling."
Lando Norris and Stoffel Vandoorne swapped MCL33 cockpits today as the Briton got behind the wheel of the car with the updated aero package, and the Belgian took over tyre testing duties for Pirelli with the previous-spec chassis.
Norris continued the test programme that Vandoorne started yesterday, correlating further aero data on the new components, and testing a variety of set-up changes with different tyre compounds and fuel loads.
Other than a quick pit-stop at Turn Two with a minor setting issue, for which the car needed to be recovered back to the pits, there were no other issues or car damage to report, and the scheduled run plan was concluded successfully.
Vandoorne completed a full programme with the Pirelli test car, finishing his running mid-afternoon having clocked just shy of 100 laps. He and the team were satisfied with the programme development and the data gathered.
"Today wasn't about testing while doing flat-out qualifying or race-spec driving as such," said Norris, "it was more about aero tests. It was also all about keeping it on the track, which I didn't quite do - a little spin into the entry of Turn 12, but nothing major - to be consistent and complete the tests for the team. With these updates and going to Monaco next, there are some things the team is trying to work on that are very important for future races.
"There are definitely some differences in the two specs - positive in many ways, but there are still some things with the old one that are also positive, so it's all about combining the two which will make the car even faster. In general, there's more downforce and it's good to have the confidence to push in Turns One, Two, and Three - the high-speed corners. Overall, it's definitely been a step forward.
"Jumping from F2 is still a fairly large step, and it does take a bit of time to get used to it. There are definitely things we need to improve and work on, but the car is still very good to drive. It does give me a lot of confidence to carry the throttle and I don't think I'm on the limit yet.
"This test has been a very good opportunity for me to get up-to-date with this car and the new power unit. It's good that I can show the team what I can do, but I see it more as an opportunity for me to keep learning and developing, and learn from both Stoffel and Fernando over race weekends, rather than proving that I can do a lap-time."
"It was a good day," added Vandoorne, "and we covered a lot of laps in a relatively short period. We were testing for Pirelli to help them develop the tyres, but also for me it was good to be back in the car and deal with different changes without adjusting the set-up, and that was definitely a useful exercise.
"Today's running was also valuable as I was able to get a little bit of a feel for the comparison between the two packages, as today I reverted back to the older spec. It meant I could see like-for-like what the improvements are in the new package and how they affect the car performance.
"The upgrades have behaved as they should, and I definitely feel that we made a step forward here this weekend."
"Today we completed another solid day of running with both cars," said Eric Boullier. "Lando benefitted from the experience of running in the updated MCL33 package for the very first time, and once again provided useful feedback. The team will now work on analysing the information to aid our development of the new components and to correlate our on-track findings with the numbers predicted in our simulations at the factory.
"Likewise, both Stoffel and Pirelli reported a positive day of tyre testing, and they completed a full and comprehensive run plan. Stoffel's feedback on the handling of the car is also valuable to the team as a useful point of comparison between the previous-spec aero package on the Pirelli car and the new MCL33 components which he raced all weekend.
"I'm pleased to report we've completed two full test days with two cars and with no major issues. The data gathered has armed us with a lot of important information as we head into a very busy racing period leading up the summer break."
Kevin Magnussen took the wheel of the VF-18 and after teammate Romain Grosjean logged 129 laps Tuesday, the Dane tallied 75 laps at the venue where he finished sixth in last Sunday's Spanish Grand Prix.
Magnussen's best time was a 1:18.274 on his 41st lap while utilizing the hypersoft tyres. The time placed Magnussen fourth overall. Comparatively, Grosjean's best time from Tuesday was a 1:18.449, also set on hypersofts.
The morning run plan for Magnussen consisted of early reconnaissance laps followed by ongoing setup work. After an installation lap on the hards, he made a three-lap stint on a used set of mediums before reverting back to the hards for a three-lap jaunt.
Next up was a pair of eight-lap outings on the supersofts, with a switch to hypersofts for three stints, each of which came on fresh rubber to maximize performance.
Magnussen completed the morning session on used mediums for another eight laps and closed for the mandatory lunch break with 53 laps in the bag.
He was limited to only 22 laps in the afternoon as a pneumatic pressure issue sidelined him just 90 minutes into the session. But in those 22 laps, he ran three stints on the softs that totaled 19 laps before a switch to the baseline hards for three laps.
"I had a good day today," said the Dane. "We were mainly testing tyre items. There were lots of interesting things done. We obviously had some kind of issue at the end, which sadly meant we had to stop for the rest of the day. That's still being investigated. All in all though, it was a good day with some good mileage, especially learning more with the tyres."
Force India brought the test to a close with development driver, Nikita Mazepin, in the car, while third driver Nicholas Latifi worked with Pirelli.
"It's always a pleasure to be in the car," said Mazepin, "and, as always, I have tried to deliver the best job I could in the most professional way.
"The conditions are very different compared to the last time I drove the VJM11 during the winter. The car feels so much better now and from the first moment I could feel the positive step the team made. I had my reference points from my work in the simulator so it wasn't all new for me, but it still felt much more consistent and easy to drive compared to pre-season testing.
"Our programme today included a mix of long and shorter runs working mainly on the softs and hypersoft. We had a small issue in the morning that prevented us from running as much as we would have liked, but we were able to catch up in the afternoon."
"It was good to have Nikita in the car again after his outing in pre-season," added chief race engineer, Tom McCullough. "It's always interesting to see a young driver grow with the team and his maiden win in GP3 last weekend showed how much he has developed over the last few years.
"Nikita was up to speed quickly thanks to his work in the simulator and helped us gather some important data. We had a productive day, even though a hydraulic leak caused us to lose some time after our aero runs in the morning. We were able to repair the car and go back out for two more runs before lunch and we adjusted our plan to make up for lost ground in the afternoon.
"We managed to complete all our test items, which was very important for the team ahead of Monaco. Looking at both days, it's been a valuable session that will help us develop the VJM11 even more as the season progresses."
Renault concluded the test with third & reserve driver Jack Aitken taking to the wheel of the R.S.18 for the first time.
He completed 128 laps with a 1:18.942 being his fastest time of the day and sixth quickest overall. The day consisted of a variety of aero and mechanical evaluations over a range of stint lengths as Aitken became acclimatised to the car.
"Today was an amazing experience for me driving a contemporary F1 car for the first time," said the youngster. "I was a little surprised how quickly I adapted to the car as I was up to speed quite smoothly in the morning. It was a busy day with a packed programme! We got through it really well, with both the team and myself able to learn a lot through the day. Overall, an awesome day with a lot of laps on the board and plenty of data to analyse so I'm a happy man."
"We ran a similar programme to yesterday," added sporting director, Alan Permane, "the only exception being getting Jack acclimatised in the car. He got up to speed quickly in the morning session and ran consistently with very good feedback. As the day progressed, we began a mixture of runs on a range of tyre compounds, testing different stint lengths, as well as the usual aero and mechanical test item evaluations. Another productive day overall."
Check out our Wednesday test gallery from Barcelona, here.