The penultimate day of pre-season testing for the F1 teams saw an interesting start of the day as overnight showers had wet the track, making for some exploratory runs on intermediates when the session kicked off.
It was Esteban Ocon in the Renault RS20 who was first to venture out on track, carefully navigating around the circuit on intermediate tyres. Antonion Giovinazzi soon joined him for Alfa Romeo.
Ocon managed a best of 1m40.059s before he returned to the pits. When Bottas joined the track 13 minutes into the session, his first lap was immediately nearly 10 seconds faster, going around in 1m31.928s. Vettel came out on track moments later, but he was no match for Bottas's impressive laps on the humid track.
When Latifi also came out do so some running, he sound found himself in the gravel at Turn 12. He kept it out of the wall and returned to the pits immediately, leaving the track completely empty.
Bottas returned later to further improve his time, and it wasn't until slicks were in order that further improvements seemed possible.
Verstappen was the first to go out on slicks at 10:13. Everybody who didn't venture out in the first hour joined Verstappen in the next 30 minutes before times started to tumble towards 11 o'clock.
5 minutes past 11, the first red flag of the day was out, as Giovinazzi touched the white line on the way into Turn 4 and spun into the barrier. The session got going again 10 minutes later, but it didn't take long for another stoppage.
Bottas first nearly caused it, but it was Verstappen who beached his Red Bull RB16 at 11:35.
20 minutes later, it was Vettel who caused another red flag. The Ferrari driver just lost the rear as he started to pick up the throttle on the exit and was pitched into a spin. He got going again and is back in pitlane, but the gravel on track had to be cleared before green flagging the session again.
After those incidents, the track was largely dry, enabling Vettel to go fastest with 1m16.814s.
After the lunch break, there was the first on-track stoppage for Mercedes AMG F1. Once at Turn 5, Lewis Hamilton's W11 shut down with the driver unable to do anymore shifting. Hamilton decided to roll downhill and park his car at Turn 7. Funnily, Ferrari employee and former driver Marc Gene was watching alongside the track where Hamilton parked, and he noted the stoppage made an "interesting sound, probably an engine failure".
RED FLAG: Session interrupted and this one is on us. @LewisHamilton stops on track and the Champ heads back to the garage...— Mercedes-AMG PETRONAS F1 Team (@MercedesAMGF1) February 27, 2020
The boys already on the way to collect W11 so we can take a closer look 🛠 #F1Testing pic.twitter.com/1MgyoeqLhn
The team later revealed that the stoppage was caused by an oil pressure anomaly which made the engine shutdown as a precaution. That was it for today for Mercedes AMG F1, as the car wouldn't return to the track for the remainder of the day.
Meanwhile, others enjoyed a trouble free afternoon, with no other stoppages or interruptions, while Vettel's time from the morning wasn't challenged anymore.
This meant that Thursday was a reverse of fortunes from last week, with this time Ferrari heading the timesheet and completing a trouble free day, and Mercedes having to watch part of the afternoon from the sidelines.