ADUO: FIA confirm Mercedes granted F1 engine upgrades despite complaints from rivals over test findings

Following the introduction of all-new engines for the 2026 season, Formula 1's governing body implemented an Additional Development and Upgrade Opportunities (ADUO) system, designed to allow manufacturers to catch up to the performance of the leading power unit during the rules cycle.

It was revealed in June after the first round of performance assessment, which included the first five rounds of the season, that the FIA had adjudged Red Bull to have the strongest engine and had granted upgrades to Mercedes, Ferrari, Audi and Honda.

The FIA never revealed their findings to the media, but teams and drivers confirmed the outcome publicly, while a document revealing the results was also leaked.

The ruling was seen as controversial because the consensus in the paddock was that Mercedes, whose works team had won the first six grands prix of the season, were being given an upgrade, while Red Bull, who had managed just a single podium in that time, would potentially lose more ground to their rivals.

Red Bull driver Max Verstappen spoke out against the findings, while Mercedes team principal Toto Wolff raised further questions over the FIA's processes when he said in July that his team have "the most powerful power unit".

The FIA refrained from publicly confirming the results while a review was carried out, but now, following the second round of assessment, which concluded with the Hungarian Grand Prix ahead of the sport's summer break, the findings from both periods have been announced.

An FIA statement said: "For the first period: Mercedes were determined to be in the two to four per cent window, and will thus be allowed one additional homologation in 2026 and an additional one in 2027, together with corresponding cost cap and dyno testing increases.

"Audi, Ferrari and Honda were determined to be above four per cent, and will thus be allowed two additional homologations in 2026 and two in 2027, together with corresponding cost cap and dyno testing increases."

While this part of the FIA's statement was confirmation of information that had been leaked in June, their findings for the second period provided a further blow for Red Bull.

Had upgrades made by any of the other teams since June been adjudged to have propelled their performance beyond Red Bull's, the Milton Keynes squad could have been granted their own upgrade opportunity.

However, the statement said: "For the second period, no additional homologations were granted to any of the Power Unit Manufacturers."

That means that Red Bull are at the very least seen to be performing within two per cent of the best engine, and may well still be adjudged to have the strongest power unit.

Mercedes' Kimi Antonelli leads his team-mate George Russell and Ferrari's Lewis Hamilton by 59 points at the top of the drivers' standings, while Verstappen is 130 points back from the Italian in sixth.

Mercedes are 87 points clear of Ferrari at the top of the constructors' standings, while third-placed McLaren, who use a Mercedes engine, have found form with reigning world champion Lando Norris winning the last two races.

Mercedes have been free to use their 2026 upgrade since the first-round results were communicated in June, but are not thought to have done so yet. Ferrari, Audi and Honda are thought to have each introduced one of their two upgrades for 2026.

FIA director of single seater Nikolas Tombazis 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 PU Manufacturers"

The third ADUO review period commenced with the Dutch Grand Prix over the weekend, and runs until the Mexico City Grand Prix on November 1.

Formula 1 heads to Monza for Ferrari's home race at the Italian Grand Prix on September 4-6, live on Sky Sports F1. Stream Sky Sports with NOW - no contract, cancel anytime