Formula 1’s engine regulations are set for adjustment after Mercedes’ competitors successfully lobbied for a modification following a heated pre-season dispute over power unit performance.
Manufacturers including Audi, Ferrari, Red Bull and Honda questioned the current rules surrounding compression ratios, suspecting Mercedes had gained an upper hand through advanced materials engineering.
On Saturday, the FIA confirmed that it will alter how compression ratios are assessed. The updated measurement procedure will take effect on 1 June, with an additional refinement scheduled for the 2027 campaign. The governing body added that every engine supplier unanimously supported the revision.
Compression ratio refers to the difference in cylinder volume between the highest and lowest positions of the piston. In general, higher ratios translate into greater engine output.
Some paddock estimates suggested Mercedes could be benefiting by as much as three-tenths of a second per lap. However, team principal Toto Wolff downplayed the advantage, describing it as only a minimal horsepower increase — “a couple,” as he put it.
Under the 2026 engine framework introduced this season, compression ratios were capped at 16:1, reduced from the previous 18:1 limit. Initially, compliance was verified at ambient temperature.
Rival manufacturers argued that the measurement should instead be taken at operating temperature, where engines typically experience thermal expansion. As materials heat up, compression ratios usually fall slightly and competitors believed Mercedes had discovered a more effective method of minimizing that drop.
Sources indicate that FIA checks measured the Mercedes power unit at both ambient and running temperatures, with the engine remaining within the 16:1 ceiling in every instance.
From 1 June, compression ratios will be assessed at 130°C in addition to ambient conditions. Beginning next season, testing will be conducted exclusively at 130°C. This shift effectively allows engines to exceed the 16:1 threshold at room temperature, despite the original reduction being designed to make the 2026 regulations more attractive to incoming manufacturers.
The revised power-unit rules featuring an almost equal balance between internal combustion and electric power played a key role in Audi and Ford committing to F1, while Honda reversed its prior decision to exit the sport.
In its statement, the FIA emphasized that considerable effort had gone into resolving the compression ratio debate. It described the 2026 regulations as among the most substantial technical overhauls in recent history, noting that early-season testing and races had provided valuable lessons following such sweeping changes.
The governing body also confirmed that discussions remain ongoing regarding energy management systems. Drivers have voiced concerns that limited available energy has forced them into unusual driving styles. As a result, various proposals are being considered to simplify energy deployment and recovery strategies moving forward.
