FIA Closes F1 Compression‑Ratio Loophole
The governing body now requires compression measurements at 130°C on running engines, a change meant to stop systems that raise effective compression under racing conditions.
Overview
- The rule change took effect on June 1, 2026 and requires engines to measure below the 16:1 limit both when cold and when the engine oil is at 130°C.
- The revision also explicitly bans any component, system or mechanism designed to increase the compression ratio while the engine is operating.
- Paddock reports had suggested Mercedes HPP could run higher effective compression at race temperatures, but all Mercedes power units previously passed FIA legality checks and had been approved under the old measurement procedure.
- Teams face uncertainty over whether the change will alter on‑track order because power‑unit allocation rules, scheduled unit swaps and possible fuel or hardware updates could blunt any immediate performance loss.
- The FIA says from 2027 it will base compliance solely on operating‑temperature measurements, a permanent fix that aims to remove the cold/hot testing discrepancy and protect parity for new and existing engine manufacturers.