F1 Engine Rule Change: FIA Reaches Compromise Amid Mercedes Dispute

Mercedes’ rivals have secured a rule change following a pre-season technical row over engine performance. Audi, Ferrari, Red Bull and Honda had been pushing for a change in the regulation governing compression ratios on the basis they believed Mercedes had secured an advantage through clever use of materials technology.

The Dispute and the Compromise

Formula 1’s governing body, the FIA, announced on Saturday a change to the way the compression ratio is measured, set to be introduced on June 1, with a further revision for the 2027 season. The change was approved unanimously by all power-unit manufacturers as confirmed by Sky Sports.

The compression ratio, a measurement of the cylinder displacement between the two extremes of the piston stroke, directly impacts power output. Increasing the ratio typically leads to more power. The 2026 engine rules limited the ratio to 16:1, down from 18:1 in previous regulations, and initially measured this at ambient temperature.

Rivals suspected Mercedes was able to comply with the 16:1 limit at ambient temperature but increase the ratio – and therefore power output – when the engine was running hot. They pushed for compression ratio measurements to be taken at operating temperature.

How the New Rule Works

The FIA’s compromise involves measuring the compression ratio at both ambient temperature and 130 degrees Centigrade starting June 1. From 2027, the compression ratio will only be measured when the engine is at 130 degrees Centigrade. ESPN reports this allows manufacturers to potentially exceed a compression ratio of 16:1 at ambient temperature while still adhering to the regulations at operating temperature.

While estimates of the potential performance gain for Mercedes varied, Toto Wolff, Mercedes F1 boss, suggested it was a matter of “a few horsepower – in England you would say a couple, which is more like two and three.”

Background and Impact on New Manufacturers

The original reduction in the compression ratio to 16:1 was intended to make the new engine formula more accessible to newcomers like Audi and Red Bull Powertrains, and to facilitate the use of fully sustainable fuels. Autosport details the reasoning behind the initial rule change.

Audi and Ford entered F1 specifically because of these new power-unit regulations, which feature a near 50-50 split between internal combustion and electrical power. Honda also reversed a previous decision to quit the sport.

Ongoing Evaluations

The FIA statement also noted that further evaluation and technical checks on energy management matters are ongoing. Drivers have raised concerns about energy starvation leading to unusual driving techniques, and various proposals are being considered to address these issues.