Formula 1’s engine catch-up mechanism, known as ADUO, has become one of the most politically charged subjects in the paddock, despite its results not yet being officially published by the FIA.
All manufacturers were informed of the initial ADUO results during the Monaco Grand Prix weekend, meaning everyone in the paddock already knows where they stand ahead of any formal announcement.
The delay in the public announcement stems from a verification process requested by Red Bull-Ford Powertrains, who were placed at the top of the initial performance ranking by the FIA, a result that surprised those within Red Bull itself.
Red Bull team boss Laurent Mekies explained the team’s position when speaking to Autosport, stating there is “not one single data sample” in which Red Bull holds an advantage over Mercedes, prompting the request for additional scrutiny of all data, sensors and methodology.
The verification process began ahead of the Barcelona Grand Prix and was initially expected to take between seven and ten days, a timeframe that has since elapsed with communication and handling of the final outcome still to be resolved.
Mercedes falls into the category of having an ICE deficit of between two and four percent, which grants it one development token, while Ferrari, Audi and Honda are all more than four percent behind the benchmark and receive two upgrades this season and two more for next year.
Honda is understood to have the largest deficit to close of any manufacturer, though sources indicate it is no more than ten percent, which is significant because a gap larger than that would have triggered additional permitted expenditure provisions.
One of the more surprising aspects for fans is that ADUO upgrades have already appeared on track before any official public announcement, with Audi running an updated power unit in Barcelona and Ferrari introducing its first ADUO upgrade of the year at the Austrian Grand Prix.
This is permitted because the message manufacturers received from the FIA in Monaco constitutes the official green light to introduce new parts, with communication between the FIA, teams and manufacturers being the decisive factor rather than any public-facing announcement.
Red Bull is primarily challenging Mercedes’ entitlement to ADUO, which carries a degree of irony given that if Mercedes delays introducing its upgrade, it could logically keep Red Bull at the top of the ICE ranking at future assessment points.
A deeper structural issue within the ADUO system also exists, as the measurement method only considers the internal combustion engine while permitted upgrades extend to the electrical side of the power unit, and parameters such as Ferrari’s smaller turbo are not factored in despite affecting power output.
FIA single-seater director Nikolas Tombazis has acknowledged he would have been open to making the parameters somewhat more complex, though manufacturers agreed to keep the system as simple as possible when it was established in the spring of 2025.
What began as a safety net designed to help manufacturers with a sizeable performance deficit has, for now, evolved into one of the most significant political battlegrounds in the Formula 1 paddock.