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Formula 1’s governing body, the FIA, has announced a resolution to the sport’s regulatory row over engine compression ratios, with a tweak to the regulations set for June 1 and a further change in 2027.
The regulation, which stated the V6 engine’s compression ratio must not exceed 16:1 when measured cold, has been the focus of a technical dispute between Mercedes and its rivals since the start of the year.
The ratio was reduced from 18:1 to 16:1 under F1’s new power unit regulations for 2026, partly to make it easier for new manufacturers, such as Audi and Red Bull Powertrains, to compete.
But late last year Mercedes’ rivals suspected the German manufacturer, which supplies engines to its factory team, McLaren, Williams and Alpine, had engineered a way to comply with the 16:1 ratio when the engine was cold but increase the ratio – and therefore increase power output – when running hot.
Mercedes and its rivals have been involved in a dispute over engine compression ratios. Glenn Dunbar/LAT Images
The rivals proposed a hot test instead of the cold test, but the FIA put forward a compromise for 2026 in which both hot and cold tests would be performed from a set date forward.
On Saturday, the governing body confirmed an agreement had been reached that would see the compression ratio measured cold as well as when the engine is at 130 degrees Centigrade from June 1 onwards. It added that in 2027 the compression ratio would only be measured when hot.
“A significant effort has been invested in finding a solution to the topic of the compression ratio,” an FIA statement said. “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.
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“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.”
June 1 falls after the seventh round of the championship in Canada, meaning any alterations to existing power units to comply with the second test will need to be made by the eighth round in Monaco.
The FIA also confirmed it is still assessing changes to the power unit’s energy management regime ahead of the first round of the new season next weekend in Australia.
