Ferrari suspect 'special fuel' is inflating Mercedes' horsepower advantage

Ferrari believe a 'special fuel' is at the root of Mercedes' growing engine performance advantage, according to a report from Motorsport Italia — and the Scuderia are watching closely to see whether an FIA clampdown will expose the gap.

A widening engine deficit

At the start of the season, Ferrari estimated they were trailing Mercedes by approximately 20 horsepower. That figure, already a significant deficit in the modern Formula 1 era, is now feared to have grown. Ferrari 'strongly suspect' that a regulatory loophole — allegedly exploited by Mercedes over the winter — has artificially inflated the gap.

The rumour centred on a specific technique said to allow Mercedes to exceed the maximum permitted fuel compression ratio of 16:1. While the method required a 'special fuel', it reportedly delivered a meaningful boost in outright power. Crucially, the trick was undetectable under previous FIA testing protocols, adding a layer of frustration for those who suspected foul play. Estimates of the exact horsepower benefit vary, but the concern at Maranello is real.

FIA moves to close the loophole

From Monaco onwards, the FIA has changed its testing procedures, now examining engines at 130 degrees rather than at ambient temperature — a deliberate effort to close the suspected loophole. A further escalation is expected in August, when even stricter inspections could be introduced to settle the debate definitively.

For their part, the word from Mercedes' Brixworth engine facility is unequivocal: "nothing will change" with the new testing regime. Toto Wolff, who has also been vocal on broader power unit topics — including his push for a 60:40 ICE-to-ERS power split from 2027 — previously dismissed any suggestion that the team's fuel was non-compliant. However, if Mercedes are ever forced to modify their fuel formulation as a result of the tightened scrutiny, any subsequent regression in performance would be telling.

Adding intrigue to the narrative, it was reported earlier in the year that Petronas were in a 'race against time' to gain approval for Mercedes' fuel ahead of the 2026 season — a detail that has not gone unnoticed by Ferrari.

Context: Ferrari's wider power unit picture

Beyond the immediate controversy, Ferrari's situation highlights a broader challenge. While the Scuderia are regarded by many as having the best chassis on the grid — and are favourites heading into Monaco — that advantage is unlikely to translate across the full season if the engine deficit persists.

Ferrari are expecting to receive ADUO (Additional Development and Upgrade Opportunities), a new catch-up mechanism embedded in the 2026 engine regulations. However, a meaningful power unit update is still months away, leaving the team to manage the performance gap in the interim.

Also worth noting is the wider reach of the Mercedes power unit: the Silver Arrows currently supply McLaren, Alpine, and Williams in addition to their works operation — meaning any performance swing at Brixworth would have consequences felt across a significant portion of the grid.

A widening engine deficit