Under the new Formula 1 power unit regulations, discussion about the compression ratio flared up even before a single wheel had turned with the 2026 machinery. The ratio between cylinder volume with the piston at the bottom of its stroke and at the top was 18:1 under the previous regulations, but has been reduced to 16:1 for 2026 - partly to make it more accessible for newcomers.
Competitors had caught wind that Mercedes can comply with the 16:1 compression ratio during static tests, but might achieve a higher ratio at higher temperatures while the car is running. Audi, Ferrari and Honda jointly sent a letter to the FIA to ask for clarification, but after an initial meeting of technical experts on 22 January, the federation did not immediately appear to be planning any intervention.
