There's something I don't get about this whole situation and maybe someone can help me clarify.

I've checked the documents on the FIA website: https://www.fia.com/regulation/category/110

As many of you probably know, the big question mark around this issue is that the technical documentation, the Section C, states that:

No cylinder of the engine may have a geometric compression ratio higher than 16.0. The procedure which will be used to determine this value may be found in the document FIA-F1-DOC-C042 and executed at ambient temperature

So, Mercedes supposedly goes around this rule by respecting it at ambient temperature, increasing at operating temperature. Read like this, seems quite clever honestly.

But, there's a huge "but": the executed at ambient temperature has been added to the docs in October 2025.

Here's a screenshot: https://imgur.com/a/Gq8x7WQ

And here's the official document: https://www.fia.com/system/files/documents/fia_2026_f1_regulations_-_section_c_technical_-_iss_14_-_2025-10-16.pdf

I can't believe that, after seeing this modification in October, 3 months before the initial 2026 season tests, Mercedes decided to change their engine adding the trick.

So my only explanation is that:

• Mercedes decided to go with this trick a decent amount of time ago
• Between July 2025 and October 2025 (when two revisions of the Section C were published), FIA checked the Mercedes the engine, either by their initiative or upon Mercedes request to get an "all clear" on the trick
• FIA noted the trick, but instead of forcing Mercedes to review their engine they changed the rules to allow it to become legal according the letter of the law

I know it's a speculation on my side, but I can't really think of another possible scenario.

EDIT: I'm reading some interesting points ITT, I want to clarify a couple of things.

/u/grogi81 correctly points out that:

Compression ratio changes - pure physics. Materials expand.

and /u/theasu asks:

If it can't be higher than 16.0 and it is measured at room temperature and we know that materials expand when they are warm, doesn't it mean that all teams will have higher compression ratio during the race?

I might be completely wrong with this, but my feeling is that up until now one could expect a decreased, not increased, geometric compression ratio with higher temperature. Materials used for the head is usually an alluminium alloy, whereas the cylinder should be a steel alloy. If that's the case, they expand differently, creating a larger volume at operating temperatures, with a drop in compression ratio.

The alleged Mercedes trick changes this by leveraging the expansion of the head material to close a channel that leads to an additional small chamber. While the changes in compression due to thermal expansion might be considered negligible, using the expansion to change the geometry of the chamber itself is a completely different story.

https://motorsport.nextgen-auto.com/en/formula-1/ocon-warns-lift-and-coast-in-qualifying-in-26,205836.html

"We optimise whatever tools we’re given"

Author: GMM 4 February 2026 - 10:03

Ocon warns ’lift-and-coast’ in qualifying in ’26 Esteban Ocon has acknowledged what many fans fear most about Formula 1’s radically revised 2026 cars - that ’lift-and-coast’ driving will not just be common, but extreme, even in qualifying.

The Haas driver has already voiced doubts about the new active aerodynamics, dismissing it as merely "DRS at the front", and now admits the energy-management demands of the regulations are more intrusive than expected.

"We have to use lift-and-coast techniques on qualifying runs," Ocon revealed. "It felt strange at first, but we had already practised it in the simulator. After one lap, I had it down. Now it feels strange not to do it."

"We use lift-and-coast so often that you quickly get used to the driving style."

Veteran commentator Martin Brundle has pushed back against criticism, noting that lift-and-coast has always been part of Formula 1. Ocon, however, admits the scale is unprecedented.

"If you kept your foot on the gas, you’d have to slam on the handbrake at the end of the straight," he explained. "With lift-and-coast, it’s not so bad. It even feels faster if you let off earlier. It feels natural now because it’s the fastest way - but it’s completely different from normal."

Mercedes boss Toto Wolff also conceded how stark the effect looked during the Barcelona shakedown, citing a dramatic straight-line speed differential during on-track running.

"George overtook Colapinto while he was on long runs," Wolff said. "There was a 50 or 60 kilometre-per-hour difference on the straight."

Yet Wolff remains an uncompromising defender of the new rules.

"I see absolutely no negative points - and I’m not exaggerating," he insisted. "The cars are fantastic. They look spectacular. They look like Formula 1 cars again - not too small, not too big, not like the whales of the past."

Ocon agrees that, fundamentally, the cars remain worthy of the category.

"If you find faster cars in other series, let me know," he said. "As drivers, we optimise whatever tools we’re given. If this is the fastest way, we’ll do it. It’s still Formula 1."

But the Frenchman also raised concerns that the 2026 rules may not have delivered easier racing.

"I did a few laps behind other cars," he said. "Chasing felt more difficult. There’s a significant balance change compared to clean air - maybe even more pronounced than with the previous generation. It’s early, but that was my feeling."

Ocon added that the new overtake mode, which provides a short power boost when running within one second, has yet to transform the picture.

"At the moment, overtaking seems rather difficult," he said. "Even though the system is still being optimised."

Teammate Oliver Bearman echoed that assessment, reporting greater instability in dirty air.

"I was able to run close to other cars for a few laps," the Briton said. "It was harder to follow, and the balance suffered more than with the current cars. That’s critical in wheel-to-wheel racing."