A statement from the FIA said that Mercedes were “determined to be in the 2-4% window” (behind the best internal combustion engine), while Audi, Ferrari and Honda were all determined to be “above 4%”.
That means Mercedes are allowed one additional upgrade in 2026 and one in 2027, and the other manufacturers, bar Red Bull, two.
Mercedes have won eight of this season’s 12 races so far, and Red Bull, who set up a new engine design and manufacturing facility to produce an engine for this year’s new rules, none.
Nikolas Tombazis, FIA director of single-seaters, said: “The FIA has undertaken thorough and exhaustive analysis as part of our Aduo review process.
“With the release of the findings of period two, we are confident that, based on the quality of the data, its analysis is incredibly robust, giving us a high level of confidence in our findings.
“We also have to respect the confidentiality and intellectual property of the teams and their power-unit manufacturers in disseminating any details from the findings.
“This is the first year of Aduo so naturally there are areas which we may evolve over time, in discussion with all the power unit manufacturers.”