The FIA has published an update to the Formula 1 technical regulations that changes how the compression ratio of power units will be measured during the 2026 season.The discussion emerged during the pre-season period after reports suggested that Mercedes had developed an engine concept where the compression ratio could increase significantly once the unit reached operating temperature.

While the engine reportedly complied with the current limit of 16:1 during standard checks at ambient temperature, it was suggested that the ratio could rise to around 18:1 under full operating conditions.

In response, the FIA has introduced additional measurement requirements to ensure compliance across different temperature conditions.

Until 31 May 2026, the compression ratio will continue to be measured only when the engine is at ambient temperature.

From 1 June 2026 until 31 December 2026, however, the measurement must be carried out both at ambient temperature and when the engine is heated to 130°C.

The regulations also clearly state that any component, mechanism, assembly or integrated system designed to increase the compression ratio beyond 16.0 under operating conditions will be prohibited.

The delayed introduction of the rule is understood to be a compromise, giving power unit manufacturers time to adapt their engines if necessary. As a result, teams may still run the current concepts during the opening phase of the season.

This means that until the eighth race of the season in Monaco, some manufacturers could theoretically retain a performance advantage. If the situation indeed concerns Mercedes’ engine concept, the potential benefit would not only apply to the factory team but also to its customer teams (Alpine, Williams and McLaren) which all use Mercedes power units.