Nikolas Tombazis clarifies FIA’s ADUO system amid Formula 1 engine debate. FIA’s Nikolas Tombazis explains why controversial ADUO engine rules favor simplicity.

Tombazis (FIA): “For the ADUO, we only measure the thermal engine because the manufacturers wanted to keep things simple”

The FIA’s technical director has clarified one of the most debated technical topics in Formula 1 over recent weeks.

The controversial ADUO system

The first ADUO allocation of the 2026 Formula 1 season was originally expected to be announced before the Monaco Grand Prix. However, even after the Spanish Grand Prix in Barcelona, the official allocation has still not been formally published. Unofficially, teams were informed of the allocation bands during the Monaco Grand Prix weekend. According to reports circulating in the paddock, Red Bull emerged as the benchmark, while Mercedes was placed in the 2% band and Ferrari in the 4% category.

Those figures immediately sparked intense discussions behind the scenes, particularly regarding Mercedes, which has been dominating the championship. Questions quickly arose about the methodology used to determine the ADUO classifications and whether the system accurately reflects the overall performance of modern Formula 1 power units.

Why is only the combustion engine measured?

One possible explanation lies in the fact that the ADUO assessment is based exclusively on the performance of the internal combustion engine (ICE), completely excluding the electrical component of the power unit.

On this topic, FIA technical director Nikolas Tombazis provided valuable insight into how the governing body arrived at this approach. Speaking to SoyMotor, the Greek engineer explained the reasoning behind the final decision.

“The reason why the ADUO focuses on the combustion part is because there was a feeling that the electrical side would be the real battleground, the area where teams would compete and where the best solution would ultimately prevail,” explained Tombazis.

He then elaborated on the lengthy discussions that took place before the introduction of the system: “Between the end of 2025 and the beginning of 2026, there were extensive discussions to define the details of the ADUO, and we debated whether secondary parameters should be included or not.”

“For example, if the intake manifold temperature of an engine is very high, the engine will produce less power, but it will also require less cooling and therefore provide an aerodynamic advantage. Do we want to take that temperature into account? We discussed these kinds of issues and the various parameters that influence engine performance.”

According to Nikolas Tombazis, the FIA was initially open to creating a far more sophisticated measurement system. However, the power unit manufacturers strongly favoured a simpler solution: “The position of the engine manufacturers during those discussions was to keep things as simple as possible. They wanted us to focus solely on power output. We responded by saying that was acceptable to us and that we agreed with the idea of simplifying things as much as possible.”

Nikolas Tombazis stressed that the FIA ultimately adapted its approach to accommodate those requests: “We could have had a much more complex equation, but there was a desire to make it as simple as possible,” he said.

The ADUO measurement is based on a torque sensor positioned between the engine and the gearbox, with the system focusing specifically on the power generated by the internal combustion engine. Nevertheless, as Tombazis previously explained to FormulaPassion earlier this year, several corrective measures and technical safeguards are incorporated into the process to ensure the data remains as representative as possible.