On 26 August 2026, the Fédération Internationale de l’Automobile issued its formal determination covering the first and second Additional Development and Upgrade Opportunities review periods for the 2026 Formula 1 World Championship. Published under the authority of Article C4 of the 2026 Formula 1 Technical Regulations, the communication confirms continuity in the competitive order of the internal combustion engine element. Red Bull-Ford Powertrains remains the reference manufacturer, and no new homologation entitlements have been created as a result of the second assessment window. All allocations granted after the opening review remain in force and will govern development activity for the remainder of the season.
The announcement is the first practical demonstration of ADUO in operation. Introduced as a core pillar of the 2026-2030 power unit regulatory cycle, the mechanism is designed to facilitate organic convergence without resorting to artificial performance balancing. Its first full application this year is being closely watched by all five power unit manufacturers and their customer teams.
What ADUO Is Designed to Do
The 2026 power unit regulations represent the most significant reset since the introduction of the hybrid era in 2014. The formula moves to a close to 50-50 split between internal combustion and electrical power, removes the MGU-H, increases the output of the MGU-K to approximately 350kW, and mandates 100 percent advanced sustainable fuel. While the electrical architecture is largely free for continuous optimization within cost and testing constraints, the internal combustion engine itself is subject to strict homologation. Manufacturers must homologate a base ICE specification at the start of the season and are ordinarily limited to a single upgrade path thereafter.
ADUO was conceived to prevent a scenario where a fundamental combustion shortfall becomes locked in for multiple seasons. It is not a success handicap and it is not a Balance of Performance system. It does not penalize the leading manufacturer or reduce its performance. Instead, it creates a defined, transparent relief valve that allows manufacturers whose ICE falls below a measured threshold to access additional homologation opportunities, additional financial headroom under the power unit cost cap, and additional dyno testing time to address the deficit.
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The system operates on three defined assessment windows within each championship year. Its eligibility logic is deliberately narrow and objective. The FIA evaluates only the ICE component, not the complete power unit, not the energy recovery system efficiency, not battery deployment strategy, not aerodynamic integration, and not chassis performance. If a manufacturer’s ICE deficit is less than 2 percent relative to the benchmark, no relief is triggered. If the deficit is at least 2 percent but less than 4 percent, the manufacturer is entitled to one additional homologation in the current season and one additional homologation in the following season. If the deficit is 4 percent or greater, the entitlement doubles to two additional homologations in the current season and two in the following season.
There are two critical safeguards built into the regulations. First, entitlements are not cumulative within a single season. A manufacturer qualifies only on the first occasion it meets a threshold. It cannot stack allocations from period one and period two. Second, eligibility for the third period is conditional. A manufacturer that fails to qualify after the first two periods cannot become eligible as a result of the third period in that same season. This structure encourages early identification of genuine deficits while preventing opportunistic late-season claims based on circuits that may favor one combustion characteristic over another.
Financial and testing relief is graduated. For the 2 to 4 percent band, relief extends to approximately USD 3 million in additional cost cap allowance and a commensurate increase in dyno hours. The scale then increases through defined steps, reaching up to USD 11 million for deficits of 10 percent or more, with a limited provision in 2026 only to anticipate a portion of future allowances to accelerate recovery work. This is not unrestricted spending. It is ring-fenced for work directly associated with permitted ICE-related upgrades.
The list of components that may be modified under an ADUO homologation is prescriptive. It includes the internal combustion engine itself, the exhaust system, the turbocharger and wastegate assembly, associated electrical components and sensors that are integral to combustion control, elements of the energy recovery system and its cooling where they interface with the ICE, the MGU-K, control electronics, and specific hydraulic and fluid systems. The FIA’s technical department must approve the scope of each upgrade to ensure it remains within the intended combustion-core focus.
How the Benchmark Is Determined
The technical heart of ADUO is the ICE Performance Index. This is not a single power figure or a headline horsepower number. It is a composite index derived from high-frequency data logged from every power unit on the grid during Grand Prix sessions, cross-referenced with dyno correlation data supplied by the manufacturers under confidentiality agreements.
The index is constructed from four primary inputs: input shaft torque, engine speed, the measured power contribution of the MGU-K in its motor mode, and a weighting factor that reflects power sensitivity to lap time at each circuit. This last factor is essential. A 10kW advantage has a different lap time value at Monza than at Monaco. By weighting for power sensitivity, the FIA attempts to produce a circuit-agnostic view of pure combustion performance.
Critically, the methodology was developed in consultation with all power unit manufacturers over more than 18 months prior to the 2026 season. It deliberately excludes variables that would conflate ICE output with hybrid system cleverness, such as energy recovery efficiency, battery state-of-charge management, or deployment strategy. Two power units could have identical ICE output but very different lap times because of how they recover and deploy electrical energy. ADUO isolates the former.
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Data quality and confidentiality are paramount. The FIA collects data from the standard ECU and additional FIA-mandated sensors, applies correction models for fuel energy content, ambient conditions, and installation effects, and then performs the analysis in a secure environment. No absolute index values, no torque curves, and no comparative charts are released to the public or to rival manufacturers. This protects intellectual property while still allowing the regulatory outcome to be communicated.
First Review Period: The Foundation
The first ADUO review period was originally defined as rounds 1 through 6 of the 2026 championship. Owing to logistical and calendar adjustments early in the season, the FIA confirmed that it would in fact encompass the first five events: the Australian Grand Prix, Chinese Grand Prix, Japanese Grand Prix, Miami Grand Prix, and Canadian Grand Prix. The governing body committed to communicating findings no later than two weeks after the Canadian Grand Prix.
Following exhaustive analysis of that five-race sample, the FIA determined that Red Bull-Ford Powertrains had established itself as the benchmark ICE. Mercedes High Performance Powertrains was assessed as operating within the 2 to 4 percent deficit band relative to that benchmark. As a consequence, Mercedes became entitled to one additional homologation in 2026 and one in 2027, together with the associated cost cap and dyno testing increase for that band.
Audi, Ferrari, and Honda were each assessed as having a deficit in excess of 4 percent in that first window. Each therefore received the larger allocation: two additional homologations in 2026 and two further homologations in 2027, with proportionally greater financial and testing relief. This outcome meant that, heading into the European phase of the season, four of the five manufacturers on the grid held some form of ADUO entitlement, while Red Bull-Ford was the sole manufacturer operating outside the relief framework.
Several of those manufacturers moved quickly. By the time the field reached the Austrian Grand Prix, at least one of the manufacturers entitled to two upgrades had already introduced and homologated a first ADUO-driven specification, demonstrating that the additional dyno capacity and cost cap headroom could be mobilized rapidly when the technical direction was clear.
Second Review Period: Confirmation of Continuity
The second review period covered rounds 6 through 11, from the Monaco Grand Prix through to the Hungarian Grand Prix. For analytical purposes, the FIA uses cumulative data from the start of the season through the end of the relevant window, meaning the second assessment included all data from Australia through Hungary, eleven races in total. This rolling cumulative approach reduces the statistical noise of any single outlier circuit and increases confidence in the trend.
The outcome, communicated on 26 August, is one of continuity. The relative ordering established in the first period was maintained with no manufacturer moving into a different eligibility band. No manufacturer that had previously been below the 2 percent threshold fell back far enough to qualify, and no manufacturer that had qualified in the larger band improved enough to drop into the smaller band or out of eligibility entirely, nor did any manufacturer in the smaller band deteriorate enough to move into the larger band. As a result, the FIA confirmed that no additional homologation slots would be awarded as a consequence of the second period.
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This also confirms that Red Bull-Ford remains the reference ICE for a second consecutive assessment. The determination is purely technical and ICE-specific. It does not imply that Red Bull-Ford has the most powerful overall power unit or the fastest car. It means that, when the combustion element is isolated using the agreed methodology, its ICE Performance Index is the highest.
An important timing detail concerns Honda. Honda introduced a new power unit specification that made its race debut at the Dutch Grand Prix, which is round 12 of the championship. Because the second assessment window closed at the end of the Hungarian Grand Prix, that new specification fell outside the period under review and was excluded from the analysis. It will be included in the data set for the third review period.
FIA Single-Seater Director Nikolas Tombazis, addressing the process, said: “The FIA has undertaken thorough and exhaustive analysis as part of our ADUO review process. With the release of the findings of period 2, 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 decision not to publish any quantitative index figures is consistent with long-standing practice in power unit matters, where combustion efficiency, friction, and fuel interaction data are among the most sensitive areas of intellectual property in the sport.
The Separation Between ICE and Overall Performance
One of the most discussed aspects of this year’s championship has been the apparent disconnect between the ADUO standings and the championship standings. Mercedes, for example, has built a substantial advantage in both the Drivers’ and Constructors’ Championships during 2026, yet its ICE was assessed as being within the ADUO relief band. This is not a contradiction in the system. It is an intentional consequence of its design.
Contemporary Formula 1 power unit performance is a system outcome. A highly efficient energy recovery system, superior battery thermal management, more effective electrical deployment across a lap, and optimal integration with the chassis and aerodynamic package can more than compensate for a small combustion deficit. The 2026 regulations were deliberately architected to increase the relative importance of the electrical side to achieve sustainability objectives. ADUO deliberately does not attempt to equalize the complete power unit. It attempts only to ensure that a manufacturer is not permanently locked into an uncompetitive combustion core that would then make all subsequent hybrid development less effective.
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By isolating the ICE, the FIA avoids creating a de facto Balance of Performance for the entire power unit, which would disincentivize innovation on the electrical side and penalize teams that have done a better job of integrating their package.
Financial and Operational Mechanics in Practice
When a manufacturer qualifies for ADUO relief, the additional cost cap allowance is not a blank check. It is audited under the Power Unit Financial Regulations and must be attributed to eligible projects. The allowances, up to USD 3 million for the lower band and scaling to USD 11 million for deficits of 10 percent or greater, cover additional hardware, machining, materials, and staff time directly related to the permitted upgrade. In 2026 only, the regulations also permit limited forward anticipation, meaning a manufacturer with a very large deficit can bring forward a portion of future allowances to address the issue sooner.
The additional dyno testing allowance is equally important. Under normal homologation rules, power unit dyno time is tightly capped to control costs. ADUO provides a defined uplift, allowing more combustion development cycles, more turbocharger mapping work, and more validation of revised exhaust and cooling concepts. For manufacturers who have already used one of their 2026 opportunities, this extra time has been critical in ensuring reliability of the new specification before track introduction.
Unused upgrades do not roll over indefinitely. If a manufacturer is granted two upgrades for 2026 and only uses one, the second is forfeited at the end of the 2026 season. However, entitlements granted for 2027 remain available in 2027 regardless of whether the 2026 slots were used. This creates a strategic decision: deploy quickly to gain lap time this year, or hold the upgrade to target specific circuit characteristics or to align with a larger chassis package later in the season.
Manufacturer-by-Manufacturer Implications
For Red Bull-Ford Powertrains, the confirmation that it remains the benchmark means it will continue to operate within the standard homologation framework for the remainder of 2026. It cannot access ADUO relief unless a future regulatory cycle in 2027 produces a different outcome. Any further performance steps must therefore be achieved within the single standard upgrade allowance that all manufacturers receive, plus reliability fixes permitted under the regulations. The stability of its combustion performance provides a platform to focus development resources on electrical integration, drivability, and reliability.
For Mercedes High Performance Powertrains, the retention of a single additional upgrade in each of 2026 and 2027 offers tactical flexibility. Having already demonstrated strong overall power unit performance and strong chassis integration, Mercedes can choose to use its remaining 2026 slot to further close the measured combustion gap, or it can reserve development capacity for 2027, where the entitlement will carry over regardless of this year’s championship outcome.
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For Audi, Ferrari, and Honda, each holding two upgrades in 2026 and two in 2027, the strategic picture is more complex. All three have already demonstrated the ability to design, validate, and introduce a new specification under ADUO, with at least one having done so before the Austrian Grand Prix. With the second period producing no change, their remaining allocations for 2026 are fixed. They must now decide how to allocate their second 2026 slot across the remaining races. Circuits with long periods at full throttle and high power sensitivity, such as Monza or Mexico City, may reward a combustion efficiency step more than a tight street circuit. However, waiting also carries risk, as the development and homologation process itself requires lead time and the unused slot expires at the end of the season.
Honda’s position is particularly nuanced. Its new specification debuting at Zandvoort for the Dutch Grand Prix arrives just after the cut-off for the second period. That specification will be judged as part of the third period data set, which runs from the Dutch Grand Prix through the Mexico City Grand Prix. If that step proves effective in closing the ICE deficit, it could influence the starting point for 2027, but under the rules, it cannot create additional ADUO allocations for 2026 beyond those already granted, because the system is not cumulative.
Governance, Confidentiality, and Evolution
A recurring theme in Tombazis’s comments is the balance between transparency of process and confidentiality of data. The FIA has emphasized that the measurement methodology, the correction models, and the eligibility thresholds were all shared transparently with the power unit manufacturers during the development of Article C4. The application of that methodology, however, relies on data that manufacturers consider highly proprietary.
The governing body has therefore committed to communicating only the regulatory outcome — which manufacturers qualify and for how many upgrades — without publishing index values, margins, or underlying sensor traces. This approach is intended to maintain trust among competitors while still providing sufficient clarity for fans and stakeholders to understand why development opportunities have been granted.
Tombazis has also acknowledged that the first year of operation will inevitably produce lessons. Potential areas for evolution, discussed informally in the paddock, include the granularity of the power sensitivity weighting, the treatment of sustainable fuel batch variation, and the administrative timeline for communicating results to allow teams to plan freight and manufacturing. Any changes would be subject to consultation with all power unit manufacturers and would apply prospectively, not retroactively to the 2026 determinations.
Looking Ahead to the Third Window and 2027
The third and final ADUO review period of 2026 will assess performance from the Dutch Grand Prix through the Mexico City Grand Prix, covering rounds 12 through 18. Results are expected to be communicated after Mexico City. Under the regulations, this final window cannot create eligibility for any manufacturer that failed to qualify in the first two periods. Therefore, the pool of eligible manufacturers for 2026 is now closed. No new entrant can join the relief framework this season as a result of the third period. The third period can only confirm or provide additional data, but it cannot expand the number of manufacturers receiving relief.
Beyond 2026, the multi-year nature of the entitlements becomes significant. The 2027 homologation slots already granted — one for Mercedes and two each for Audi, Ferrari, and Honda — will remain available irrespective of what happens in the third period of 2026. If a manufacturer again meets the deficit thresholds during the 2027 ADUO assessments, additional slots for 2027 and 2028 may be layered on top. In a scenario where a manufacturer qualifies for the maximum allocation in two consecutive years, it could theoretically have access to four homologation opportunities in a single season: two carried over from the previous year and two newly earned. This stacking provision is intentional, designed to allow a manufacturer facing a substantial deficit to accelerate convergence over a two-year horizon.
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It is also important to remember that 2026 is the first year of a new power unit cycle that runs through 2030. Combustion development is inherently long-cycle work. Improvements made under ADUO in 2026 will form the foundation for subsequent electrical integration work in 2027 and 2028. The system is therefore best understood not as a short-term equalizer but as a structural correction mechanism that prevents early lock-in.
Why ADUO Is Not Balance of Performance
Much of the external debate has framed ADUO as a form of Balance of Performance. That characterization is inaccurate and misunderstands the intent of Article C4. Balance of Performance systems, as used in other championships, typically add weight, reduce power, or constrain aerodynamics for the leading competitor to compress the field. ADUO does none of those things. The benchmark manufacturer is not penalized, its performance is not reduced, and its development path is not restricted beyond the standard rules applicable to all.
Instead, ADUO provides additional development tools to those who are behind on a specific, narrowly defined technical metric. Success still requires those manufacturers to design, build, test, and integrate a better solution. It must then be combined with excellence in energy recovery, battery management, software, cooling, chassis integration, and race operation to translate into lap time. As Tombazis has noted previously, the system is not a magic bullet. The most competitive overall power unit must still be produced on merit.
This distinction matters for the long-term health of the sport. By avoiding artificial equalization of the complete package, the regulations preserve the incentive for all manufacturers to innovate across the entire hybrid system while providing a safety net that ensures a combustion shortfall does not become a terminal disadvantage for the entire regulatory cycle.
The FIA’s confirmation of the second ADUO period results therefore establishes continuity rather than disruption. The allocations remain as set after the first five races, Red Bull-Ford remains the reference, and the remaining manufacturers retain defined, audited pathways to continue their combustion development within the cost cap.
As the championship moves into its final overseas leg, attention will now turn to how those remaining homologation opportunities are used, how Honda’s new specification performs when it enters the data set at Zandvoort, and how the lessons from this inaugural year will shape the evolution of the mechanism for 2027 and beyond.
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