Mercedes rivals pushing to change engine compression measurement procedure?

The new-for-2026 regulations mandate a 16:1 compression ratio for the internal combustion engine, while the measurement is done at ambient temperatures when the engine is off.

But Mercedes have reportedly found a way to pass the FIA measurements but then increasing their engine compression to 18:1 once it is running with the car on track, which is worth quite a bit of performance.

The initial reports claimed both Mercedes and Red Bull Ford Powertrains have exploited the same loophole, but the spotlight on the latter manufacturer has since faded, with Mercedes remaining the focus of the controversy.

The FIA has since held several meetings with the stakeholders but have been adamant that the measuring procedure will not change.

However, according to a report in The Race, Mercedes rivals, namely Audi, Ferrari, and Honda, have been working together to try and force a change in the FIA's measurement procedure ahead of the opening race in Melbourne on March 8.

The proposal will present a new procedure to measure the engine compression while hot using sensors in the car, which would result in Mercedes failing the tests.

Any changes need to be voted on by stakeholders to be applied, and the aforementioned manufacturers are looking to put the idea for a vote within the Power Unit Advisory Committee (PUAC) and are rumored to have gained the support of Red Bull, who have reportedly given up on the idea, having failed to achieve the same gains as Mercedes.

For now, the FIA seem to be firm with their stance regarding the testing procedure, while Mercedes boss Toto Wolff is adamant his team's power unit is fully compliant with the letter of the rules.

There is one issue to point out, and that is it may be too late to introduce any changes, as the power units have been homologated back in March, which makes it impossible to change the engine design before the season starts.