Overview
- From 1 June 2026, engines must meet the 16:1 limit when measured cold at ambient temperature and when heated to 130°C, shifting to hot-only checks in 2027.
- Article C5.4.3 was revised to define the new measurement windows and to outlaw any component or mechanism that increases the operating compression ratio beyond 16.0.
- The implementation was accelerated from an initially floated August start after an e-vote by the World Motor Sport Council and all five power-unit makers approved the change.
- Rivals had questioned whether Mercedes gained performance under hot running; Mercedes maintains compliance, and Toto Wolff called the row a “storm in a teacup.”
- The June enforcement falls between the Canadian and Monaco Grands Prix, giving Mercedes and its customers McLaren, Williams and Alpine seven races to ensure conformity as the FIA continues separate energy-management reviews.