‘Senior F1 insiders’ confirm Toto Wolff was right all along about Mercedes engine legality

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Mercedes’ 2026 F1 power unit has already passed the FIA’s new fuel compression ratio test, according to a report.

The off-season has been dominated by accusations that Mercedes were breaching the 2026 technical regulations, which limit the fuel compression ratio to 16:1 (down from 18:1 in the previous rulebook).

It was said that the Silver Arrows had found a loophole, passing the FIA’s room-temperature checks but exceeding the limit while out on track. There is a general provision in the rules that every competitor must be compliant at all times, but there was no way of proving the alleged breach.

That’s why Mercedes’ rivals pushed for a new test to be introduced while the engine was hot (130 degrees celsius). This was originally expected to come in from 1 August, but has now been brought forward to 1 June.

Mercedes’ engine has already passed the FIA’s new test

Speaking to Sky Sports at the start of the month, Toto Wolff emphatically stated that his team were in full compliance with the rules.

Reports suggest that Mercedes received assurances from the FIA engine boss that they wouldn’t be penalised.

“The power unit is legal,” Wolff said. “The power unit corresponds to how the regulations are written. The power unit corresponds to how the checks are being done. The power unit corresponds to how these things are measured in any other vehicle.”

Are Mercedes’ rivals hiding behind 2026 ‘excuses’?

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As ‘senior F1 insiders’ confirmed to BBC Sport, the FIA have already tested the Mercedes engine ‘at both ambient and operating temperature’. In both cases, it was under the fuel compression ratio limit.

It seems, then, that Wolff was right to declare the saga a ‘storm in a teacup’ (as he did during testing). The new test will formally kick in from the Monaco Grand Prix onwards, and room-temperature checks will no longer take place in 2027.

Was Mercedes’ 2026 engine measured incorrectly by the FIA?

Ferrari team principal Fred Vasseur called the FIA ’embarrassing’, slamming the lack of clarity as the new season quickly approached. But now it looks unlikely that the mid-season change will have a discernible effect on the pecking order.

Mercedes’ rivals have questioned the FIA’s methods after hearing that the W17 passed the new assessment. They suspect that the engine was mistakenly measured in the wrong conditions.

But Mercedes are completely confident that the clampdown won’t make a difference. They enter the season as the title favourites, with engine customers McLaren perhaps slightly behind Ferrari in third.