Overview
- Amendments to Article C5.4.3 were approved unanimously by e‑vote of the World Motor Sport Council with concurrent unanimous backing from all five power‑unit manufacturers.
- From June 1, 2026, engines must pass the 16:1 compression‑ratio limit in both ambient and 130°C conditions, with checks moving to hot‑only from 2027.
- The revision advances an originally targeted August rollout and lands between the Canadian and Monaco grands prix, giving teams seven races to adapt.
- The updated rule explicitly bans any component or arrangement designed to raise compression ratio in operation, and manufacturers’ test methods require FIA approval.
- Rivals including Audi, Ferrari and Honda had questioned Mercedes’ thermal‑behavior advantage, which Mercedes denies, while the FIA continues to review energy‑management issues highlighted in testing.