George Russell was fastest for Mercedes on the first day of Formula 1's final 2026 testing event as Ferrari hit significant trouble for the first time in pre-season when Lewis Hamilton's running was limited by a technical issue.
Russell's time of 1:33.459s at the Bahrain International Circuit bettered the fastest lap - set by his team-mate Kimi Antonelli - at last week's three-day test at the same venue, which has held two official testing events after F1's all-new cars for 2026 debuted together in Barcelona last month.
The Brit edged out McLaren's Oscar Piastri by just 0.010s after they both drove in the faster evening conditions, with the reigning constructors' champions also enjoying a strong day as reigning world champion Lando Norris was half a second back in fourth.
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Ferrari had run without suffering any notable issues in their six days of track time at the previous events, but after Charles Leclerc had impressed in the morning session - delivering a lap that kept him third on the timesheet at the end of the day - Hamilton missed 90 minutes of the afternoon with a technical issue before returning for the final stages.
Ferrari weren't the only member of the big four to face an issue on Wednesday, with Red Bull's Isack Hadjar having managed just 13 laps in the morning session because of a water system issue, before getting in a full afternoon's running as his team-mate Max Verstappen sat out ahead of his own full day in the cockpit on Thursday.
That meant it was Mercedes and McLaren who had the more solid days of the teams expected to be competing for wins and titles this season. Russell and Antonelli ensured Mercedes topped the mileage chart with a combined 145 laps, while McLaren totalled a solid 124 trips around the Sakhir circuit.
The big four teams occupied the top seven places on the timesheet, with Hamilton, who still completed 44 laps, eight tenths off the pace in the last of those positions.
Hamilton said: "It was a solid day, as we managed to complete a good amount of running, which is positive.
"We had a small issue during my session, but the team did a great job to get me back out on track to do some long runs.
"I feel like we've made progress compared to last week and I'm continuing to build my understanding of the car. We're still working on fine-tuning the balance, but we're moving in the right direction."
Suggestions that the top four will start the timesheet clear of the rest of the field were reflected in Williams' Carlos Sainz being a further eight tenths back from Hamilton in eighth.
Elsewhere, Aston Martin continued to struggle as an issue limited Fernando Alonso to 28 laps in the morning, before a spin into the gravel contributed to Lance Stroll only managing 26 laps in the afternoon.
Despite their limited running, Aston Martin were at least able to go more than two seconds faster than they had managed last week in Bahrain, with the team playing catch-up after a late arrival in Barcelona.
2026 newcomers Cadillac were once more challenged by reliability problems as Sergio Perez managed just 24 laps in the morning, but they did at least finish the day on track as Valtteri Bottas added 35 laps.
New start procedure trialled | FIA make engine rule-change proposal
The day ended with a trial of a new start procedure amid concerns the new power units for 2026 require more time to be prepared for lights out than the previous guidelines allowed for.
An additional five-second pause was added between the last car lining up on the grid and the start light procedure beginning.
The trial followed a day of significant meetings in Bahrain, with the sports bosses coming together in Bahrain to iron out several issues before the season starts for real with the Australian Grand Prix from March 6-8.
Also announced on Wednesday afternoon was that the FIA have proposed a mid-season rule change to its engine regulations that will be voted on by the five power unit manufacturers before the Melbourne race.
After rival manufacturers had spent the pre-season questioning the legality of Mercedes' power unit amid a dispute over a loophole regarding the compression ratio limit, the FIA has proposed a rule-change that will come into force during the sport's summer break in August.
While the current regulations mean the compression ratio is only measured when cars are stationary at ambient temperature, technically allowing them to exceed it when running on track, the proposal is for a new system that would also provide a measurement when the engine is at operating temperature.
The proposal has been presented to the power unit manufacturers - Mercedes, Red Bull, Ferrari, Honda and Audi - to vote one, with a super majority needed for the new test to be implemented at the start of August.
For a super majority to be reached, six of the seven voters - which include the FIA and Formula 1 along with manufacturers - would need to be aligned.
Sky Sports F1's Bahrain Testing schedule
Thursday February 19
- 6.50am-11.05am: Morning session Live
- 11.55am-4.10pm: Afternoon session Live
- 8pm: Testing Wrap
Friday February 20
- 6.50am-11.05am: Morning session Live
- 11.55am-4.10pm: Afternoon session Live
- 8pm: Testing Wrap
Watch every race of the 2026 F1 season live on Sky Sports, starting with the Australian Grand Prix from March 6-8. Stream Sky Sports with NOW - no contract, cancel anytime
(c) Sky Sports 2026: F1 Bahrain testing: George Russell fastest on first day of final test as Lewis Hamilton suffers first Ferrari pre-season issue
