Formula 1’s 2026 season has not even begun, but controversy isn’t far from the world’s most loved motorsport either. The Fédération Internationale de l’Automobile (FIA) intended to begin a new era in 2026 with new regulations, but it has already seen firefighting.
At the bottom of the whole controversy is the term’ compression ratio’ and how it is measured.
Compression Ratio Loophole
The compression ratio of an engine is the ratio of its maximum to minimum volumes, i.e., when the piston is at top dead center versus when it is closest to the crank. In sporting terms, the ratio gives us an idea of how powerful an engine is. The higher the ratio, the greater its power.
The FIA determines the maximum permissible compression ratios for engines, which all competing teams must follow. Since 2014, F1 cars have used 1,000-horsepower engines with a permissible compression ratio of 18:1.
Starting in 2026, the compression ratio has been reduced to 16:1 to attract more teams to the sport. The intended result has been achieved with Audi and Cadillac launching their own teams, while Honda is returning as an engine supplier.
As per FIA regulations, this compression ratio is measured at ambient temperature. A controversy has erupted after Mercedes and Red Bull found ways to increase the compression ratio on track.
Could the grid be finalized for 2026 before the season even begins? Image credit: F1
Why is this engine an issue?
A running engine produces heat, which expands its metal body, thereby increasing its compression ratio. This is true for engines used in both normal cars and F1 cars. The reason other F1 teams are unhappy with this is that Mercedes and Red Bull are close to achieving compression ratios of 18:1 with their engines.
A higher compression ratio means Mercedes and Red Bull can extract more power from the same amount of fuel than their competitors. Under the 2026 rules, the FIA determines the fuel flow into the engine, giving Mercedes and Red Bull a distinct advantage.
The advantage depends on how much higher their compression ratio is than their peers’. If it does reach 18:1, it could translate into an extra 10-15 hp, or a few tenths of a second per lap, which is significant in F1.
Moreover, the advantage will extend to teams that use Mercedes and Red Bull engines, effectively setting up the grid even before the season begins.
What can be done?
The ball is now in FIA’s court. Changes to engine design have long lead times and may not be possible for either Mercedes/ RedBull or others to incorporate before engines are homologated for the 2026 season by March 1st.
The governing body seems to be sticking to the written rules rather than seeking new interpretations. In a statement, the FIA clarified that, even though limits on compression ratio have changed, the methods for making these measurements remain the same.
In effect, it says that compression ratios will only be measured at ambient temperatures, and that’s where compliance matters.
The FIA is left with two options. Either penalize Mercedes and Red Bull for exploiting a loophole, which the former has reportedly been working on for over a year. Red Bull likely achieved a similar result by hiring an engineer from Mercedes earlier this year.
The other is to allow other teams to catch up during the season through additional upgrades, while Mercedes/ Red Bull make the first half of the season a cake walk with their superior engines. This means see teams going up in arms from the first practice of the new F1 era.
Can a compromise be reached within the next three months? It will be interesting to see how this pans out.
This report contains information that appeared in Motorsport, GrandPrix, and Ars Technica.