What happened on day four of F1's secretive 2026 shakedown

Aston Martin finally appeared on track in the latter stages of the fourth day of the Barcelona Formula 1 shakedown, while Mercedes kept collecting miles and McLaren's day was cut short with trouble.

Fresh from turning over 90 laps apiece on Wednesday, Andrea Kimi Antonelli and George Russell traded turns again on Thursday with a combination of long runs and shorter outings to get on top of various power unit modes.

Russell was unofficially fastest with a 1m16.4s, but rather than being fooled by flashy headlines about fastest laps or alleged benchmark times, the big-ticket item in Barcelona is gathering data and mileage, and that has been an area Mercedes has been undeniably strong at.

It meant Mercedes has now used up its three test days allowed in Barcelona and can head home knowing it will have turned by far the most laps out of all the teams with its W17, which has run reliably throughout and earned positive feedback from its drivers.

"We go [to Bahrain testing] with high confidence and high hopes because, definitely, it's been good," said Antonelli. "Obviously, we had our issues during the shakedown, but we were able to fix them and now we can be sure that in Bahrain we can more or less hit the ground running there as well."

On the other side of the spectrum, Aston Martin only just made it out on day four after flying its car to the track on Wednesday, having previously announced it wanted to delay its shakedown appearance to get its AMR26 in working order.

George Russell, Mercedes

Photo by: Mercedes AMG

In the hands of Lance Stroll, the unpainted Adrian Newey-designed AMR26 finally broke cover to turn a total of five laps in the final hour, sporting what looked like an intriguingly unique sidepod and engine cover design compared to its rivals.

Stroll caused a late red flag by grinding to a halt mere minutes before the projected 6pm local time finish of the session. Fernando Alonso is expected in the Honda-powered car on Friday's fifth and final day of the shakedown week.

Oscar Piastri took over the new McLaren MCL40 from team-mate and defending world champion Lando Norris on the second day of running for the 2026 McLaren. After 48 laps the Australian remained in the garage during the afternoon after the team encountered a fuel system issue which required an investigation.

“It was nice to be back out today, especially in the new car," Piastri reported. "There’s a lot of challenges this year up and down the grid, so it was good to get stuck in. We had a fuel system issue, which cut our day short, but the team’s working hard to get that fixed and back out tomorrow."

McLaren's technical director for performance, Mark Temple, added: "The car is very complex, so we decided to bring the car back into the garage and strip it down to fully understand where the problem is coming from, ahead of tomorrow’s running."

Oscar Piastri, McLaren

Photo by: McLaren

After only being able to run in the wet on Tuesday, Lewis Hamilton reconvened with his the Ferrari SF-26 and said it was "amazing" to run 85 laps in the dry, despite suffering an early spin out of Turn 11 on his out-lap as his cold tyres struggled with the chilly Catalan circuit. Charles Leclerc added another 89 laps in the afternoon as Ferrari squeezed past Mercedes in Thursday's lap charts.

Another morning runner was Liam Lawson in the Racing Bulls VCARB 03, a team which has now also used up its three-day allowance. After a low-key debut on Monday, Cadillac returned for its second day with Sergio Perez behind the wheel.

Alpine, Audi, Haas and Red Bull all sat out the Thursday running and are expected on track again on Friday. In Red Bull's case, the team is understood to have flown spare parts over from Milton Keynes to help repair the damage from Isack Hadjar's crash on Tuesday.

Barcelona F1 shakedown - Day 4 lap counts