FIA Confirms Legality of Mercedes and Red Bull Engine Innovation Ahead of 2026 Rules
A fresh technical debate has erupted in Formula 1 just weeks after the conclusion of the 2025 season, with Mercedes and Red Bull once again at the centre of attention as preparations intensify for the sport’s major 2026 regulation overhaul.
The controversy surrounds a novel engine concept developed by both teams that appears to push the limits of the FIA’s compression ratio regulations. Under the upcoming rules, power units are subject to a maximum compression ratio of 16.0:1, a figure verified through static testing when cars are stationary in the garage at standard ambient temperatures.
However, Mercedes and Red Bull have reportedly identified a way to effectively exceed this threshold once the engine is operating on track. By exploiting temperature-related behaviour within specific internal components, the manufacturers are able to achieve a higher compression ratio during running conditions—unlocking additional horsepower without breaching the written regulations.
How the concept works
At the heart of the issue is the distinction between static and dynamic testing. Like all engine suppliers, Mercedes and Red Bull remain fully compliant with the compression ratio limit during FIA inspections carried out at room temperature. Yet when the power unit reaches operating temperatures on track, thermal expansion allows certain components to behave differently, resulting in an increased effective compression ratio.
This principle is not new to Formula 1. Comparable scenarios have emerged in the past, most notably during the flexi-wing debate earlier in the season, where aerodynamic components passed all static load tests but flexed under real-world racing forces to deliver performance gains.
As always, Formula 1 engineering thrives on finding performance in the margins. Especially at the beginning of a new regulatory era, teams are more willing to explore creative interpretations of the rules, even if it means venturing into grey areas.
FIA grants approval
The development quickly drew attention from rival manufacturers. Ferrari, Honda, and Audi are understood to have jointly approached the FIA seeking clarification on whether such an approach complied with the spirit and intent of the regulations.
According to reports from it.motorsport, the FIA has now confirmed that the solution is legal, provided that all mandatory tests are passed under the established static conditions. With no regulation explicitly governing compression behaviour at elevated operating temperatures, the governing body found no grounds to intervene.
This outcome was not entirely unexpected. Mercedes, in particular, is believed to have engaged in extensive dialogue with the FIA during the development phase, ensuring that their concept aligned with the regulatory framework before committing significant resources to it.
Given that level of transparency, the FIA was unlikely to reverse its position after the fact—especially on an innovation that had already undergone scrutiny.
Mercedes lead, Red Bull follow
While both teams are benefitting from the solution, Mercedes are widely considered to be the originators of the idea. Red Bull, meanwhile, are thought to have adopted a similar approach after gaining insight through the influx of technical personnel recruited from Mercedes in recent seasons.
This pattern is familiar in Formula 1, where knowledge transfer—within legal boundaries—often accelerates the spread of innovations across the grid.
What happens next?
The focus now shifts to how competitors respond. In theory, rival teams could attempt to challenge the legality of the engines by lodging a formal protest at the opening race of the 2026 season in Australia. However, such a move would face significant hurdles.
Penalising six teams—four Mercedes-powered and two Red Bull-powered—on the eve of a new regulation cycle would be highly disruptive and politically complex. Moreover, Mercedes’ documented cooperation with the FIA would make any retrospective action difficult to justify.
More likely, other manufacturers will decide whether the potential performance gain justifies the cost and complexity of replicating the concept. While power unit development budgets are constrained, engine performance will remain a critical battleground throughout 2026, leaving ample opportunity for rivals to catch up.
An evolving landscape
The true performance advantage offered by this innovation remains unclear. Gains may be modest, and the competitive balance will depend on a wide range of factors beyond compression ratios alone.
What is certain, however, is that this episode highlights Formula 1’s enduring identity as a sport driven by technical ingenuity. As teams prepare for the next era, pushing regulatory boundaries—while staying just within them—will continue to define success.
Despite the FIA’s ruling, the engine story for 2026 is far from settled. With development races already underway behind the scenes, the fight for power unit supremacy is only just beginning.
