A loophole in the technical regulations has now been closed by the FIA – with the Monaco Grand Prix set to be the first race under the new system.
The Monaco Grand Prix will be the first F1 race governed by the new technical regulations, which aimed to close the loophole in Mercedes’ power unit compression ratio.
Before the season started, reports surfaced that Mercedes HPP had discovered a method to increase the compression ratio of its engine to 18:1, exceeding the 16:1 limit stipulated in the rules.
Initially, the ratio was supposed to be checked only at ambient temperatures in the pit-lane, leaving room for higher ratios during actual on-track performance, leading to backlash from rival manufacturers.
In response to the outcry, the FIA revised the regulations effective June 1st, with the compression ratio now monitored at an engine ambient temperature of 130 degrees to ensure compliance.
Mercedes reportedly utilized heat-expanding metals in their engine design to reach the 18:1 compression ratio, prompting the closure of the loophole before the European leg of the season, starting with the Monaco Grand Prix.
Despite winning all five races so far in 2026 and holding a substantial lead in the constructors’ championship, Mercedes anticipates challenges from competitors with the Additional Development and Upgrade Opportunities (ADUO) system allowing teams to narrow the gap in performance.
