Mercedes F1 Power Unit Compression Ratio Trick Legal… for 13 Races

The 2026 Formula One season has commenced as the teams have been participating in two pre-season tests. There have been several storylines developing. Among them the teams’ ability to get on top of the new regulations. In addition, there has been plenty of chatter about the Mercedes F1 power unit. More specifically, about the engine’s ‘variable’ compression ratio trick.

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As a Reminder

Mercedes has, according to reports, managed to exploit a loophole in the technical regs. For 2026 the compression ratio of the V6 engine has been dropped from 18:1 down to 16:1; a test that is carried out at ambient temperature. However, Mercedes has managed to increase the ratio under hot conditions, reportedly through manipulating metallic structures during 3D printing, which meets the test, but not the ‘spirit’ of the legislations.

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As a result, McLaren, Williams, and Alpine (ie the Merc powered teams) will have an unfair advantage over their rivals. Understandably, other power-unit manufacturers – Ferrari, Audi, Honda, and Red Bull-Ford – are unhappy and have been united and vocal in their opposition.

A Compromise

There was talk that the ‘opposition’ wanted the rules changed before the season starts in Australia on 8 March. That would leave Mercedes in the unenviable position of having to change a fundamental part of its engine design in a really short space of time. But that will not take place. The F1 Commission and the F1 Power Unit Advisory Committee met at the pre-season test in Bahrain to discuss, among other things, the compression loophole. A statement after the meeting reads:

“Over recent weeks and months, the FIA and the power unit manufacturers have collaboratively developed a methodology to quantify how the compression ratio changes from ambient to operating conditions. Following validation of this approach, a proposal has been submitted whereby, from August 1, 2026, compliance with the compression ratio limit must be demonstrated not only at ambient conditions, but also at a representative operating temperature of 130°C.”

This gives the producer of the Mercedes F1 power unit months to come up with a solution. It also give the Mercedes-powered teams 13 races (of 24) to enjoy any advantage they gain from this.

The FIA statement ended: “The vote has been submitted to the power unit manufacturers, and its outcome is expected within the next 10 days and will be communicated in due course.”