The FIA has finalized new rules for the 2026 Formula 1 engine formula, specifically addressing the contentious compression ratio issue that pitted Mercedes against its rivals. The core change mandates that the 16:1 compression ratio be measured both cold and hot, a compromise that Mercedes can accept. This dual measurement prevents competitors from exploiting temperature differences to exceed the limit during static tests, as Mercedes was alleged to have done.

The move comes after rivals, led by Audi, protested Mercedes' apparent ability to achieve a higher ratio when the engine warmed up, arguing the existing rules were ambiguous. The FIA, citing the need for clearer regulations to uphold the 16:1 limit as a core objective, approved the change unanimously. The rule takes effect from June 1st, accelerating the original August 1st date to resolve the dispute before the season opener in Melbourne.