Reports of Mercedes exploiting the compression ratio loophole with the 2026 power unit started circling the paddock weeks after the 2025 season ended. Amid speculation and complaints from the rivals, FIA has now reportedly decided to clamp down on the loophole by making changes to the test.
Going into the 2026 season, FIA introduced all-new power unit regulations, which brought the compression ratio down from 18:1 to 16:1. However, as per the FIA, the compression ratio test was set to take place at ambient temperatures, i.e., a lot colder than the operating temperatures.
Mercedes reportedly exploited the loophole and used materials that expanded as the engines reached operating temperatures, and hence increased the compression ratio, giving a performance advantage. Red Bull also got knowledge of the loophole from an employee moving to Milton-Keynes from Brackley and implemented the loophole.
Ferrari, Honda, and Audi filed a complaint with the FIA and wanted clarification on the loophole. As per the latest report from Corriere dello Sport, FIA has taken action on the complaint and is set to make changes to the compression ratio test. Starting in Australia, the compression ratio test will be performed at operating temperatures by statically heating the internal combustion engine.
A vote is reported to take place on the same day and doesn’t require unanimity, but rather a majority. FIA, F1, and four of the five manufacturers are required to form a majority. Red Bull, which was previously neutral in the matter have reportedly decided to join the rivals.
Mercedes failed to win a championship in the ground effect era, which started in 2022. However, the last time around, there was a major engine overhaul, and the Brackley outfit came out on top. The said compression ratio was believed to be worth 15 horsepower, and around 0.3 seconds of advantage depending on the track. The Brackley-based outfit came out as the favorites after the Barcelona test.
Not only is Mercedes going to lose the said advantage, but they would also have to redesign the engines to pass the test. The materials that expanded once the engines reached operating temperature would need to be substituted. With the season just a month away, this would require immense resources with no guarantee of success.
Mercedes power units completed the most laps at the Barcelona preseason test with 1136 laps split amongst Mercedes, Alpine, and McLaren with minimal reliability issues. If the engine is to be redesigned by Mercedes, the power unit learnings from Barcelona go to waste, along with no guarantee of reliability.
Former Red Bull Team Principal Christian Horner shared his take on the Mercedes compression ratio loophole
Christian Horner, who was sacked by Red Bull midway through the 2025 season, recently featured on the Today Show. The Briton was questioned about the compression ratio loophole that Mercedes is exploiting and was asked for his take on the “cheating”.
“That’s a big statement. Look, F1 is about pushing the boundaries, it’s about how you interpret the regulations. Always has been and always will be. Teams that are most conservative are the teams that are never at the front of the grid,” said Christian Horner
“You’ve got to be pushing the envelope, and of course it’s all about how you interpret regulations. Some of the brightest engineers on the planet will be looking at those regulations and think, ‘Okay, how can I maximize performance?’” he added
Toto Wolff came out the W17’s official launch and claimed the engine was legal as he asked the rivals to ‘get their sh*t together’.
Edited by Pranay Bhagi
