The FIA has confirmed that all five engine manufacturers have agreed to a change to the engine regulations relating to compression ratios effective from 1 June.

As previously reported, under the regulations overhaul the compression ratio was reduced to 16:1 this year, however it was claimed that Mercedes - and initially Red Bull - had exploited a loophole in the regulations which allowed the German manufacturer's power units to reach 18:1. This was because the measurement was taken in static conditions, however once running at temperature the Mercedes was able to reach 18:1, thereby giving it a performance advantage and also aiding fuel consumption.

At the recent meeting of the F1 Commission the manufacturers were given notice of an e-vote on whether, from 1 August, the compression ratio would be measured not only in ambient conditions, but also at a representative operating temperature of 130 degrees C.

This morning (Saturday), the FIA issued the following statement:

"A significant effort has been invested in finding a solution to the topic of the compression ratio. This parameter, which was one of the key fundamental targets of these regulations in order to attract newcomers to the sport, is limited in the regulations to 16:1, measured in cold conditions.

"The FIA has worked to find a compromise solution which determines that the compression ratio will be controlled in both hot and cold conditions from 1 June 2026, and subsequently only in the operating conditions (130deg C) from 2027 onwards."

Article C5.4.3 of the latest technical regulations now reads: No cylinder, as referred to by C5.1.3, of the Engine may have a geometric compression ratio higher than 16.0, measured in the following conditions:

• Until 31 May 2026: when the Engine is at ambient temperature

• From 1 June 2026 to 31 December 2026: when the Engine is at ambient temperature as well as when the Engine is at 130degC. Any component, assembly, mechanism, or integrated arrangement of components that is designed or functions to increase the compression ratio in operating conditions beyond 16.0 is prohibited.

The procedure which will be used to assess compliance with this article must be defined by each PU Manufacturer according to the instructions detailed in the document FIA-F1-DOC-042. This procedure must be approved by the FIA Technical Department and included in the PU Manufacturer homologation dossier.

[Note: The FIA-F1-DOC-042 will be revised in accordance with the requirements coming into force on 1 June 2026. Consequently, the PU Manufacturer's procedure shall be updated, and the PU Homologation dossier amended accordingly.]

Whereas the original 1 August deadline came at the beginning of the summer break, the revised 1 June deadline falls between the Canadian and Monaco rounds.

Insisting that it will continue to evaluate data throughout the opening rounds of the season, the FIA, in acknowledgment of ongoing concerns over energy harvesting, added that "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 learnings to be taken from pre-season testing and the initial rounds of the 2026 championship.

Further evaluation and technical checks on energy management matters are ongoing.