Formula One's governing body, the Fédération Internationale de l'Automobile (FIA), has reached a unanimous agreement with power unit manufacturers to tighten the way engine compression ratios are controlled from June 1, 2026.
The decision comes after a tense technical dispute during pre-season testing in Barcelona and Bahrain, where rival teams suspected the Mercedes-AMG Petronas Formula One Team of exploiting a regulatory gray area within the new 16:1 compression ratio limit.
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rules explained
Under the comprehensive 2026 power unit rules, one of the most significant technical overhauls in recent history, the engines are capped at a compression ratio of 16:1.
Compression ratio determines how strongly the piston compresses the air-fuel mixture before ignition, which directly affects combustion efficiency and power output. Higher ratios can produce better performance but also increase engineering complexity and regulatory sensitivity.
Initially, compliance with the 16:1 limit was measured only at “ambient temperature” (cold conditions). This led to allegations that some teams engineered components to expand or behave differently under extreme operating heat, potentially allowing the engines to pass static inspection while still providing higher performance on track.
Mercedes has consistently ensured that its power units fully comply with the regulations.
What changes from June 1st?
After consultation with manufacturers, the FIA confirmed that from 1 June, compression ratios will be tested in both cold and hot operating conditions.
From the 2027 season onwards, testing will be conducted exclusively in hot conditions, effectively closing any interpretive flaws associated with thermal expansion characteristics.
There are seven races left before the new enforcement protocols go into effect.
In a statement, the FIA acknowledged the magnitude of the regulatory change:
“The regulations introduced for 2026 represent one of the biggest changes in recent memory. All parties acknowledge that with the introduction of such significant regulatory changes, there are collective lessons to be learned from pre-season testing and the early stages of the 2026 championship.
“Further assessment and technical investigation on energy management matters is ongoing.”
This adjustment reinforces Formula One's commitment to regulatory clarity and competitive equity as the sport enters a new engine era.
