Upgrade the Leader, Ground the Laggard: The Paradox of FIA’s ADUO Test
The FIA’s second Additional Development and Upgrade Opportunities (ADUO) test has produced a result that looks increasingly difficult to reconcile with what is happening on track: Red Bull, drawing on the expertise of former Honda employees, has been identified as the benchmark for internal combustion engine (ICE) performance, while championship leader Mercedes is classified as a manufacturer lagging behind.
Following an analysis of ICE performance from the Australian to the Hungarian Grand Prix, Mercedes was found to be 2-4% behind Red Bull, while Audi, Ferrari, and Honda were more than 4% behind. Under the ADUO regulations, this means Mercedes receives one token for each of the 2026 and 2027 seasons, while Ferrari, Audi, and Honda get two. The allowances apply to the power unit (PU) manufacturers, meaning Mercedes’ allocation affects four teams – Mercedes, McLaren, Alpine, and Williams – while Ferrari’s covers Ferrari, Haas, and Cadillac. Honda supplies Aston Martin, Audi supplies its factory team, and Red Bull Ford Powertrains supplies Red Bull and Racing Bulls.
In other words, the manufacturer leading the championship is allowed to develop its PU, while the manufacturer whose car is currently only the fourth-fastest cannot. The reason lies in what ADUO actually measures: the system evaluates only ICE performance, rather than the performance of the complete PU.
The ADUO allowances come with additional financial and testing resources:
For a 2-4% deficit: USD 3 million and 70 test bench hours;
For a 4-6% deficit: USD 4.65 million and 100 test bench hours;
For a 6-8% deficit: USD 6.35 million and 150 test bench hours;
For a 8-10% deficit: USD 8 million and 190 test bench hours.
The first measurement was taken after the first five races of the season, before Monaco. The results were the same, with Mercedes lagging behind Red Bull by 2%, Ferrari and Audi by 4-6%, and Honda by 6-8%. The second test concluded after Hungary. The last ADUO test period of the 2026 season is scheduled for Races 12-18 (The Netherlands to Mexico).
The problem is that an ICE does not exist in isolation. In the 2026 regulations, the electric side of the PU and energy deployment have become just as important, while the performance of the car also depends heavily on aerodynamics, downforce, chassis performance, and tyre behaviour.
Red Bull is currently the fourth-fastest car, and its results have been far from satisfying due to a lack of downforce, battery performance, and overall aerodynamic effectiveness, but it will not be able to upgrade. Mercedes, meanwhile, is leading the championship and is allowed to upgrade. Yet, in Belgium, Mercedes team principal Toto Wolff said Mercedes has “the most powerful power unit” on the grid, with Red Bull team principal Laurent Mekies agreeing. Because of the measurement method, Mercedes is formally allowed to catch up with Red Bull, while it is clearly visible on track that everybody else is trying to catch up with Mercedes, which has been the strongest team since the season kicked off in Melbourne.
The decision to measure only the ICE was made by the manufacturers themselves in spring 2025. At least four of the five manufacturers must agree to any changes in the methodology. The 2026 regulations have fundamentally changed the role of the electric side, as the ICE and battery now contribute 50% each. It is questionable not to take the electronic part into account, since batteries have been a major factor since the hybrid era, not to mention the new 2026 regulations with their controversial “yo-yo racing” and super-clipping effects. The batteries are planned to be removed only by 2030, as FIA President Mohammed Ben Sulayem, following widespread criticism from drivers and fans alike, has expressed his wish for the much-loved V8 engines to return around that time.
For the manufacturers classified as lagging, ADUO does provide a route to catch up. Ferrari is already preparing its second major power improvement within ADUO for Monza, September 4-6, which is expected to produce an additional 10 hp (around 7 kW), while the first upgrade, presented in Austria, was rumoured to have brought 7 hp. However, maximum power is clearly not enough, as the electric part is supposed to provide power to the end of the straights, while the rear tyres should not overheat. More ICE power alone may not close the gap if the weakness lies elsewhere in the PU or the car itself.
ADUO was introduced with a clear objective: to prevent one manufacturer from dominating the new regulations. Yet the first and second tests have produced a peculiar situation. Red Bull, whose car is currently struggling to compete for victories, has been identified as the benchmark and cannot receive additional development opportunities. Mercedes, which leads the championship and has been the strongest package on the straights, is formally classified as a laggard and can continue to develop, making it more difficult for the current second-place team, Ferrari, to catch up. Red Bull has already tried to convince the FIA to review the conclusions, but repeated tests following the first measurement period produced no change.
The issue, therefore, is likely that ADUO is measuring only one part of what makes a modern power unit competitive.