Despite the huge technical changes, the new cars, and the new tyres, there were some familiar names at the top of the timesheets as Mercedes and Red Bull's drivers occupied the top four places at the end of Friday's testing action at the Circuit de Barcelona-Catalunya.
The afternoon had started off in artificially damp conditions, with trucks pouring water onto the track surface over the lunch break. Despite the drivers running full Wets and Intermediate Pirelli tyres to start the afternoon, the conditions dried up quickly – so much so that the slick Mediums and Softs were used in the final hour.
Lewis Hamilton finished the day with the quickest time of the test, setting a 1:19.138 in the closing minutes as he experimented on the Soft (C4) compound for three separate fast runs. Having initially gone quickest with a 1:19.141, Hamilton improved on this time with just 10 minutes remaining to find 0.003 seconds on his final fast run.
George Russell, who topped the morning session, finished the day in second place. He used the C5 compound to set a 1:19.233 just before the lunch break – the then-fastest time of the test. It was a strong final day from Mercedes, as they logged 160 laps of the circuit between their two drivers as well as claiming a 1-2 at the top.
Red Bull weren't far behind, either. Sergio Perez, driving the afternoon session, put in a 1:19.556 on the Soft (C4 compound) to finish in third, fractionally ahead of teammate Max Verstappen. The reigning World Champion clocked a 1:19.756 on the Medium (C3) tyre during his 59 lap shift in the morning – this time was good enough to keep him fourth in the standings at the final chequered flag. Red Bull put in 133 laps in total between their two drivers during the day.
Aston Martin's Sebastian Vettel, who posted a 1:19.824 on the Soft (C4) tyre in the morning, placed in fifth, a tenth behind Verstappen. But Aston Martin's day was cut off early as Vettel came to a halt on track just before the lunch break. The team weren't able to fix the issue, which was an oil leak, and the car didn't rejoin the action in the afternoon.
Ferrari were sixth and seventh with Charles Leclerc and Carlos Sainz respectively, on what was the most low-key day of the test for the Scuderia. The team put in 136 laps between their two drivers over the course of Friday's running.
More reliability issues hit the new cars
With the teams seemingly cranking up the pace a little on the final day, there were numerous red flag interruptions that disrupted the morning session.
Alpine's Fernando Alonso brought out the first red flag as he came to a very smoky halt on track less than one hour into the morning. While the car was recovered to the pits, the team confirmed that a hydraulic issue was the cause of his stoppage. The car couldn't be repaired in time to rejoin the track, meaning Alpine's Barcelona test came to a premature end.
Pierre Gasly became the first driver to crash during testing, as he lost control of his AlphaTauri and went off into the barriers in the morning. With Gasly unhurt, the session was stopped while the car was retrieved. Their day also came to a premature end as a result.
Shortly after Gasly's crash, Alfa Romeo's Guanyu Zhou brought out the red flags once again as he spun at the beginning of the final hour of the morning. The car was brought back to the pits and, shortly after the session resumed, Zhou was back on the circuit. However, it appeared all was not well with the C42, as Zhou almost immediately broke down again – triggering the fourth red flag of the morning.
Vettel's stoppage then brought out the red flags again just before the lunch break, with his day also ending as a result, while there were also issues for Haas and Nikita Mazepin.
With Haas running a plain white livery after pulling the Uralkali branding from their car and their trucks, Mazepin had only completed nine laps of the circuit when he encountered a suspected leak in the VF-22. He withdrew to the garage, and wasn't seen again for the day.
With F1 pre-season testing getting underway in Barcelona this week, our journalists Dieter Rencken, Mike Seymour and Thomas Maher look ahead to what to expect.