The crucial final test of Formula 1's 2026 pre-season test is underway with plenty of key developments on and off the track.

We've rounded up the biggest things we've learned from day one of the second Bahrain test.

The field is closing up

Watching trackside on the first day of last week’s Bahrain test exposed big differences from car to car. But with every team making big strides forward, the differences are now far more subtle.

That’s to be expected given the depth of understanding teams now have both of the energy demands and the dynamic characteristics of their cars.

While it’s still difficult to be certain exactly how wide the competitive spread is, and the gap of 3.339s from the fastest to the slowest car today likely compresses the field more than it will be in Australia, it illustrates not only how quickly teams have got more on top of the cars, but also that the worst fears about a rules overhaul creating big gaps will not be realised. - Edd Straw

Start procedure trial

An experimental new start procedure was trialled at the end of the opening day of the test, as F1 collectively tries to work out a solution to the peculiar preparation required with the new 2026 engines.

There was a five-second hold once the grid was lined up for a practice start on Wednesday before the normal start procedure began. This is designed to give all drivers enough time to build the boost level in their engines' turbos by revving the engine in advance.

It requires around 10 seconds to do that so there were concerns about how to manage this with a normal sequence, whereby cars filter into their grid positions gradually and then the start sequence begins with a random hold before the red lights go out.

The five-second trial was a compromise as teams will still need to refine their own techniques – it's not as simple as 'rev the car for as long as this procedure lasts, then everything's easy'.

This was highlighted by McLaren conducting full practice start simulations in the pitlane - including a 35-second wait with the engine idling to replicate the scenario of sitting waiting on the grid.

It shows how much refinement is still going on even this deep into testing. - Scott Mitchell-Malm

Upgraded Mercedes looks fast

Mercedes gave the first hint it really can live up to its pre-season favourite tag by making its best trackside impression of testing so far on Wednesday, having debuted a suite of new upgrades.

The car looked extremely well poised on a nine-lap George Russell run I watched from trackside in the evening, and I was not surprised to learn that the stint was extremely competitive – three tenths a lap faster than Isack Hadjar in the Red Bull, whose run on the same compound was four laps shorter.

Plans can vary so much that it’s hard to know if a light fuel load flattered the Mercedes, but this is the information we have to work with today – and more importantly, we watched the Mercedes plenty on shorter runs last week, too.

It didn’t look this good then. And while it might be tempting to think the sandbags have been lifted, it’s how the car behaves dynamically on track that caught the eye today rather than ultra-impressive straightline speed or deployment hints for example.

This suggests this was Mercedes benefitting from time sorting the chassis out than suddenly showing what its engine is really capable of – even though that could of course be part of it. - SMM

Expect new ratio test mid-season

Formula 1 is heading towards a mid-season rule change – as the row over compression ratios took a twist in Bahrain.

Following the push from Mercedes’ rivals to close down an advantage it is said to have, the FIA is to hold an e-vote next week on new test procedures to come into play over the summer break.

While the specifics of the new test has not been revealed, the hope of Ferrari, Audi, Honda and Red Bull is that the new 130°C checks will close off any trick that Mercedes has in play.

And all indications point towards the proposed tweak to the checks getting voted through – with the FIA clearly keen to get a line drawn under the matter before the Australian Grand Prix.

How much this will impact Mercedes’ engines after the new tests come into play is not known, and that is something which will only become clear in the long term.

However, what the state of affairs does mean is that Mercedes and its customer teams will hold on to their original advantage for at least the first 13 races of the campaign. - Jon Noble

How rear lights will be used

F1 cars have new rear lights and sequences for 2026.

Though there's also the addition of amber safety lights on the mirrors - to warn other drivers when a car has slowed to below 20km/h or stopped - what's changed at the rear is all to do with signalling how the MGU-K is being used to deploy power or charge the battery.

There are three different ways this can be used. A single red flash denotes the MGU-K is delivering less than the full 350kW of power; two flashes means the MGU-K is not delivering any power but isn't recharging; and multiple fast flashes means the MGU-K is recharging while the engine is still running flat-out - more commonly known in the F1 paddock as 'super clipping'. (There's a full explainer of that here.)

The rear wing endplate lights, which flash red, mirror the pattern of the rear impact structure light - which is now an oval shape, rather than rectangular, to save around 180g.

That red rear impact structure light is also used for other reduced-speed scenarios, including during a safety or virtual safety car period, or as a rain light when the car is using intermediate or wet tyres.

The light can also still turn blue if a driver does not have a full superlicence, like when a driver only eligible for a free practice licence stands in during FP1. - SMM

Ferrari has an eye-catching upgrade

Ferrari's quietly impressive 2026 pre-season has continued with a solid opening day of the final test - 114 laps logged between Charles Leclerc and Lewis Hamilton.

But the most eye-catching part of its Wednesday was the new diffuser wing it debuted.

It appears to be a clever solution for the 2026 beam wing ban and debuting it so close to the Melbourne season opener, gives its rivals little time to copy, should it prove successful. - Josh Suttill

Aston Martin's 2026 will get worse before it gets better

Fernando Alonso says "there's a solution in place" for Aston Martin's woes as "nothing is impossible to fix".

But the exact timeline of that solution is unclear and, until then, it's looking like there is plenty more pain on the way for the team after a bruising start to 2026.

Why Lance Stroll spun off at the Turn 11 left-hander remains unclear, but the team once again completed the fewest laps of any team on Wednesday.

That's far from ideal for a team that probably needs mileage more than any other right now.

It's rapidly running out of time to avoid being left scrapping to get out of Q1 in Melbourne - or to ensure the reliability to get both cars to the finish. - JS

Verstappen's car criticism isn't relenting

Max Verstappen called F1’s new regulations “Formula E on steroids”, “anti-racing” and “not Formula 1” last week. His frustration with having to keep one eye on the battery constantly remains, as when asked in today’s press conference he suggested that the hybrid had no place in F1 and should be left to Formula E - albeit with the caveat that he called the upcoming Gen4 FE machine “a very cool car”.

“I want us to stay away from that and be Formula 1,” said Verstappen. “So don't increase the battery, actually get rid of that and focus on a nice engine.”

He also stressed that he has no intention of holding back when asked his opinion, and rightly so. When The Race questioned whether there was any pushback from F1 itself on his opinions, or any effort to get him more on-message, he reiterated his desire to speak his mind.

“I'm just sharing my opinion,” he said. “ "We live in a free world, free speech and that's what I felt. Not everyone needs to feel like that but that's what I felt.

"Also it doesn't matter what other people have to say about that, I got a question and I shared my opinion. That I'm allowed to do. It's not about receiving pushback or whatever. I was just being honest." - ES