Update Revealed on Mercedes Engine Rule Controversy as Rivals Push for Change

It has not been the simplest start to the year for Mercedes.

News at the back end of last-year seemed to prop up the fact that the German team was the front-runner for 2026, with the shift in regulations seeming to benefit the Brackley-based squad.

Mercedes finished second in the Constructors' Championship in 2025, but Red Bull's second driver conundrum hindered the Austrian team in terms of proper representation in the team standings.

After the recent news that teams were examining whether Mercedes and Red Bull had broken any rules with their 2026 cars - and Toto Wolff swiftly responded - it seems like a further development could add even more instability to Mercedes in the near future.

Red Bull turn on Mercedes in surprising twist

2025 was the first year since 2020 that Max Verstappen has not led Red Bull to a Drivers' title. | Red Bull Content Pool

A recent report from The Race seems to confirm that it is Mercedes backed up against a wall now, as news has emerged that Red Bull has been swayed in terms of their stance on F1's compression ratio limit.

Both Mercedes and Red Bull have been highlighted for allegedly breaking the 16:1 ratio, which means that the duo could potentially get more power out of the car at higher speeds, something they have apparently been able to do thanks to the FIA's testing only being in place when the car is stationary and the engine is cool.

Ferrari, Audi and Honda have written an open letter to the FIA in the past week, and according to reports, it now seems as if Red Bull is on board with enforcing a rule change that can close the compression ratio loophole.

The Mercedes car might look good, but in other teams' eyes, it might not even be legal. | Mercedes-Benz Media

For a rule change to be implemented immediately, it needs four of five manufacturers plus FIA and FOM backing, which is unlikely due to the fact that, according to Toto Wolff, the FIA agrees with Mercedes' interpretation of the rules.

"The power unit is legal [and it] corresponds to how the regulations are written, [and] how the checks are being done... Communication with the FIA was very positive all along. And it's not only on compression ratio, but on other [topics] too."
Wolff on Mercedes' car and the FIA

The fact that four out of the five constructors are lobbying for the rule to be adapted indicates that in the future it is likely the rule will either be tweaked, or that other teams will follow in Mercedes' footsteps, the fact that neither the FIA or FOM (who almost always vote together) are on board might mean any new implementation would come into place for 2027, not 2026.

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