The ground-effect regulations are barely cold, yet off-season drama has already erupted around the 2026 engine regulations.
With good reason, as Mercedes and Red Bull Racing have found a loophole that could give them a significant advantage over their competitors come the next campaign. And according to Motorsport, this has been approved by the FIA, Formula 1’s governing body.
What is the compression ratio, and why does it matter?
An engine’s compression ratio compares the volume inside a cylinder when the piston, a moving part inside the engine, is at its lowest point, versus when the piston is at its highest point. It defines how tightly the air-fuel mixture is squeezed before ignition.
Once ignited, the expanding gases force the piston downward. This transmits energy through the connecting rod to the crankshaft, which then turns into rotational motion of the wheels. Essentially, a chain of moving parts that together generate performance.
The higher the ratio, the more tightly the air-fuel mixture is squeezed, allowing for more efficient or stronger combustion. The benefits of a higher compression ratio are clear: improved thermal efficiency, greater energy extraction from the same amount of fuel, and an increase in power output.
On the race track, this can translate into stronger acceleration, higher top speed on the straights, and improved energy deployment over a lap. Some sources are suggesting that the teams using this higher compression ratio can gain up to 0.4 seconds per lap. That Mercedes and Red Bull found a way to legally exploit the ratio could have significant implications.
FIA’s 2026 regulation loophole and how it will affect teams until 2027
Two teams, Mercedes and Red Bull, have found a way to dance around the FIA’s regulations by way of a technicality. In 2025, the mandated compression ratio was 18:1, and it was written as such in Article 5.4.6: “No cylinder of the engine may have a geometric compression ratio higher than 18.0.”
However, the governing body mandated a new compression ratio for the upcoming season and rewrote the article into the following: “No cylinder of the engine may have a geometric compression ratio higher than 16.0. The procedure which will be used to determine this value may be found in the document FIA-F1-DOC-C042 and executed at ambient temperature.”
By adding a condition in which the compression ratio is to be measured – when the engine is at ambient temperature – it opened a grey area where the ratio doesn’t have to remain the same at all times.
Now, both teams are looking to benefit from a loophole that sees the compression ratio measure 16:1 when the engine is cold, while potentially increasing towards 18:1 as operating temperatures rise.
Ferrari, Honda, and Audi flagged this compression ordeal to the FIA, hoping for an intervention by the governing body. Instead, both teams’ engines were approved; with engine concepts already locked in and production timelines well underway, it’s highly unlikely that there will be any regulatory changes before 2027.
Either way, teams can’t switch up their engine concept this close to the season start, as it’s an elongated process. Time will tell if Mercedes and Red Bull have gotten it right; with the German outfit supplying the engine to McLaren, Williams, and Alpine, multiple teams could benefit from this advantage. The other teams will likely have to make do with the tools they have until 2027.
