The FIA has published the ADUO values following the second assessment period, confirming that Red Bull remains credited with the best internal combustion engine on the Formula 1 grid. Mercedes sits between 2% and 4% behind the benchmark, while Ferrari, Audi and Honda remain more than 4% adrift.
The countdown had already begun at the end of the Canadian Grand Prix, when the first assessment period concluded. However, Red Bull’s request for the data to be reviewed prompted the FIA to take more time before publishing the results. With the second assessment period now also complete, the official ADUO classification has finally been confirmed.
Red Bull remains the benchmark in the FIA ADUO ranking
Just as it did at the end of the first assessment period, the FIA has confirmed that, according to the criteria used to compile the ADUO figures, the strongest internal combustion engine on the grid is not Mercedes’ but the unit developed by Red Bull.
That came as something of a surprise even to the Milton Keynes team. Red Bull had repeatedly maintained that its own analysis placed its engine behind Mercedes, and those concerns were also among the reasons why publication of the results was delayed after the first assessment period.
Red Bull’s aggressive recruitment policy has ultimately paid dividends. The operation succeeded in attracting some of the best engineers from rival manufacturers, including several former Honda personnel after the Japanese company had decided to close its Formula 1 project. As a result, a manufacturer that had never previously built its own Formula 1 engine has become the reference point for the rest of the grid.
“The FIA has conducted a thorough and exhaustive analysis as part of our ADUO review process. With the publication of the Period 2 results, we are confident that, based on the quality of the data, the resulting analysis is incredibly robust, which gives us a high level of confidence in our conclusions. This is the first year of ADUO, so it is natural that there are areas that we may evolve over time, in consultation with all PU manufacturers,” Nikolas Tombazis explained when announcing the results.
Mercedes remains in the 2–4% ADUO band
Although Mercedes introduced Power Unit updates in Austria with the sole objective of improving reliability, they clearly did not produce a significant increase in outright power. Mercedes therefore remains in the first ADUO concession band, covering deficits between 2% and 4%, which corresponds to a shortfall of at least around ten horsepower.
It is important to remember that ADUO figures are calculated exclusively from recorded data relating to the pure power output of the internal combustion engine. They therefore do not represent a complete picture of overall Power Unit efficiency or of how the combustion engine interacts with the electrical side of the hybrid system.
By falling into the first ADUO band, Mercedes will benefit from a $3 million relaxation of the cost-cap limit and an additional 70 hours of dyno testing. The manufacturer will also be allowed to homologate one new revised unit covering the 2026 and 2027 seasons.
Ferrari remains more than 4% behind the leading F1 engine
Ferrari’s position was arguably the most eagerly awaited. Among the leading teams, the Maranello squad has shown the clearest signs of suffering from an engine deficit during the opening part of the season. Initially, the main question was not whether Ferrari would qualify for ADUO concessions, but rather which performance band it would fall into.
For intellectual-property reasons, and to avoid providing competitors with too many reference points, the FIA has not published Ferrari’s exact band. What has been confirmed is that the deficit remains above 4%, meaning Ferrari is entitled to two engine updates per season.
Ferrari has already introduced its first stage of Power Unit development and, despite the increase in horsepower, the deficit remains greater than 4%. Maranello intends to reduce that margin further with the second homologation, which is expected to arrive at Monza.
The next step is particularly important because Ferrari is preparing its ADUO-2 specification for the Italian Grand Prix. Recent work in Maranello has also included the final phase of ADUO-2 engine testing ahead of Monza.
Because Ferrari remains more than 4% behind the benchmark, the Scuderia will receive an increase in its permitted spending limit of at least $4.65 million together with more than 100 additional dyno-testing hours. The development will form another important part of Ferrari’s wider 2026 technical programme.
Audi also falls into the ADUO band above 4%
A similar situation applies to Audi, which is credited with the fourth-best engine on the grid and, like Ferrari, falls into the band covering deficits greater than 4%.
As team principal Mattia Binotto had already explained, the German manufacturer does not expect to close the gap completely next season. Instead, Audi hopes to reach the level of the other leading manufacturers by 2028.
Audi introduced its first updated unit in Spain in an effort to improve reliability. However, it does not plan to bring a second evolution during the current season, with the next update instead scheduled for 2027.
Honda faces the biggest engine deficit
Honda is undoubtedly in the most difficult position. The Japanese manufacturer sits at the bottom of the Power Unit ranking and is significantly further behind its rivals.
Honda introduced its updated engine at Zandvoort, after the conclusion of the second ADUO assessment period, bringing an increase in power. Nevertheless, there is still a long way to go.
The update represents a first step towards 2027, as Honda does not intend to introduce any further major developments during the remainder of the 2026 season, despite having two homologations available.
ADUO concessions based on engine performance deficit
The FIA’s ADUO regulations provide different levels of additional budget allowance, dyno testing and homologation opportunities depending on how far a manufacturer’s combustion engine is behind the best-performing unit.
- 2% ≤ deficit < 4%: $3,000,000 additional budget allowance, 70 extra dyno hours and one new homologation during 2026 and 2027.
- 4% ≤ deficit < 6%: $4,650,000 additional budget allowance, 110 extra dyno hours and two new homologations during 2026 and 2027.
- 6% ≤ deficit < 8%: $6,350,000 additional budget allowance, 150 extra dyno hours and two new homologations during 2026 and 2027.
- 8% ≤ deficit < 10%: $8,000,000 additional budget allowance, 190 extra dyno hours and two new homologations during 2026 and 2027.
- Deficit ≥ 10%: $11,000,000 additional budget allowance, 230 extra dyno hours and two new homologations during 2026 and 2027.
What manufacturers can upgrade under ADUO
It is important to clarify that ADUO is not a Balance of Performance system like the one used in the World Endurance Championship. It simply gives manufacturers greater scope to develop their Power Units through additional financial resources, increased testing time and the opportunity to homologate one or more new units. The FIA does not intervene directly to equalise performance.
It therefore remains the responsibility of each manufacturer to design and develop a better engine by making effective use of the additional time and money it has been granted.
The areas manufacturers are permitted to modify under ADUO are listed in Table 1 of Appendix C4 of the Technical Regulations. They cover a relatively broad range of components, particularly those related to the internal combustion engine, exhaust system, turbocharger and wastegate valve. These are in addition to changes that remain permitted even for manufacturers that do not qualify for concessions.
Although electrical performance is not taken into account when establishing the ADUO power figures, manufacturers are also permitted to update several elements of the MGU-K, the battery, the control electronics associated with the electrical system and other hybrid components.
Components classified as FIA standard parts remain excluded. These include the high-pressure fuel pump and monitoring sensors, which are supplied by a common manufacturer selected by the governing body through a tender process.
How the FIA measures engine performance for ADUO
The regulations do not publicly specify exactly how ADUO performance is measured because the detailed methodology is contained in a separate document available only to the teams.
The FIA has, however, explained that its evaluation is based on a range of parameters measured both on the dyno and on track. These include crankshaft torque, engine speed and MGU-K power, with the data collected through sensors that are more accurate than those used in the past.
In practical terms, a torque sensor positioned between the gearbox and the engine measures the relevant parameters. The electrical contribution is then removed from the calculation, leaving only the values produced by the internal combustion engine.
At every Grand Prix, the best-performing car from each Power Unit manufacturer is analysed over a series of laps. This produces figures and statistics that can then be compared across several races before an average is calculated at the end of the assessment window.
There are certain sections of a lap where the internal combustion engine has a greater influence on performance. For that reason, the collected values are corrected by applying a form of weighting. This is also one of the elements that can differentiate manufacturers, because the final parameter takes account of power rather than overall efficiency or the way the combustion engine interacts with the electrical components.
Why hybrid interaction makes ADUO measurement complicated
This distinction is important because every internal combustion engine has its own characteristics, and the way it works together with the electrical system can vary significantly from one Power Unit to another.
As FIA single-seater director Nikolas Tombazis previously explained, the measurements give greater weight to what happens during the initial part of a straight than to the final section. Towards the end of a straight, the recorded values are more heavily influenced by the aerodynamic characteristics of the car itself.
The general outline of this model has been shared with the teams, but not its precise details, in order to prevent manufacturers from finding ways to circumvent the assessment process.
That distinction is particularly relevant as manufacturers continue developing their cars and Power Units independently. Ferrari, for example, has combined its engine programme with wider SF-26 aerodynamic development, while ADUO calculations remain focused specifically on the combustion engine rather than the complete performance of the car.
FIA and manufacturers opted for a simpler ADUO formula
The governing body also explained that, during the spring of 2025, it proposed a more sophisticated formula to the Power Unit manufacturers for determining engine power figures.
The suggested methodology would have incorporated secondary parameters such as plenum temperature and turbocharger dimensions in an attempt to produce a more precise estimate of the engine’s pure power output.
The manufacturers, however, preferred to retain a simpler system without additional corrections. That methodology now forms the basis of the ADUO assessment that has placed Red Bull at the top, Mercedes within the 2–4% deficit band and Ferrari, Audi and Honda more than 4% behind the benchmark.
For Ferrari, the result provides additional development resources as the team prepares for its next Power Unit homologation at the 2026 Italian Grand Prix at Monza, where reducing the engine deficit will be one of the key technical objectives.
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