F1 engine manufacturers and FIA approve tweaks to compression ratio checks

Formula 1's governing body the FIA says the series' power unit manufacturers have unanimously approved changes to how engine compression ratios are measured, with revisions coming as early as 1 June.

The compression ratio of the V6 combustion engines, which measures how much the air-fuel mixture inside a cylinder can be compressed, has been reduced to 16:1 for this generation of power units - partly to help make building engines more accessible to newcomers like Audi.

But rival manufacturers, believed to be led by Audi, took issue with a clever way to comply with the 16:1 compression ratio in cold and static conditions, which is how it is measured by the FIA, while expanding it under hot, running conditions and gaining a significant advantage. Audi was joined by Honda and Ferrari in lobbying the FIA to address the issue before the start of the 2026 season next week in Australia as it was rumoured that Mercedes had used the trick to its advantage - even though the team received reassurances its power units are fully legal.

F1's manufacturers disagreed over their interpretation of the 2026 power unit regulations

Photo by: Kym Illman / Getty Images

Following a series of discussions, the FIA put up a compromise for an e-vote among the five power unit manufacturers, which also includes Red Bull-Ford, giving all parties 10 days to vote for the proposal. That solution is to start measuring the engine compression ratios both in hot and cold conditions from 1 June, and subsequently only measuring them in operating conditions at 130C from the 2027 season onwards. The FIA has now said all manufacturers have voted for the proposal, with the changes also ratified by the FIA World Motor Sport Council.

"A significant effort has been invested in finding a solution to the topic of the compression ratio," the FIA said in a statement on Saturday morning. "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."

The revised article C5.4.3 of the 2026 technical regulations now states the following:

"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."

FIA to keep monitoring energy harvesting concerns

Speaking exclusively to Autosport, Red Bull team principal Laurent Mekies said his squad, which is producing its own power units for the first time in 2026, just wanted clarity on the matter before going into the new campaign.

“We’re asking for clarity. Tell us what we’re allowed to do, and the rest matters little: it’s essential to have a clear understanding of what is permitted, and then I believe every competitor should be free to reach the result by following the path they consider best. This applies not only to the power unit, but to everything," Mekies said.

The FIA also said it will continue evaluation data from pre-season testing and the first rounds of the season amid concerns over the draconian energy harvesting tactics drivers will have to use to optimise the new-for-2026 power units, which rely much more heavily on electric power than their predecessors.

"The regulations introduced for 2026 represent one of the biggest changes in recent memory," the statement continued. "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."