Formula 1’s governing body, the FIA, has reached a compromise with engine manufacturers over the measurement of compression ratios in the sport’s new-generation power units, resolving a dispute that threatened to overshadow the start of the 2026 season. The agreement, announced Saturday, will see compression ratios measured both at ambient temperature and 130 degrees Celsius from June 1, with a shift to measurement solely at 130 degrees Celsius for the 2027 season.
The controversy stemmed from concerns raised by Audi, Ferrari, Red Bull and Honda that Mercedes had exploited a loophole in the regulations to gain a performance advantage. The 2026 engine rules reduced the permissible compression ratio from 18:1 to 16:1, measured in cold conditions, partly to lower barriers to entry for new manufacturers like Audi and Ford. Rivals suspected Mercedes had engineered its engine to operate at a higher compression ratio when hot, thereby increasing power output without technically violating the cold-test limit.
Mercedes team boss Toto Wolff confirmed that FIA president Mohammed Ben Sulayem had been supportive throughout the dispute. “Fortunately for Mercedes, FIA president Mohammed Ben Sulayem is on its side,” Wolff said, according to PlanetF1. The initial focus of the dispute centered on Mercedes, though Red Bull Powertrains also voiced concerns. Mercedes’ rivals proposed a hot-temperature compression ratio test to the Power Unit Advisory Committee (PUAC), which ultimately led to the compromise agreement.
The FIA stated that a “significant effort has been invested in finding a solution to the topic of the compression ratio,” adding that the 2026 regulations represent “one of the biggest changes in recent memory.” The governing body also noted that all power-unit manufacturers had unanimously approved the rule change. The compression ratio, a key determinant of engine power, measures the cylinder displacement between the extremes of the piston stroke.
Estimates of the potential performance gain for Mercedes varied, with some suggesting as much as 0.3 seconds per lap. Wolff, but, downplayed the advantage, stating it amounted to “a few horsepower – in England you would say a couple, which is more like two and three.” Despite the initial concerns, senior F1 insiders have confirmed to BBC Sport that the Mercedes engine has consistently complied with the 16:1 limit when measured at both ambient and operating temperatures.
The rule change means that from 2027, manufacturers will be able to design engines that exceed a compression ratio of 16:1 at ambient temperature, even though the reduction to 16:1 was initially intended to attract new entrants to the sport. Audi’s entry into Formula 1 was motivated by the new power-unit rules, which emphasize a near 50-50 split between internal combustion and electrical power, and Honda reversed a prior decision to withdraw from the sport based on the new regulations.
The FIA statement also indicated that further evaluation and technical checks on energy management systems are ongoing. Drivers have reported challenges with energy deployment and recovery, leading to unusual driving techniques, and various proposals are under consideration to simplify energy management within the regulations.
