Toto Wolff rules out Mercedes legal action as compression ratio furore set for critical vote

Toto Wolff has ruled out Mercedes responding to any late engine rule changes with legal action, suggesting the manufacturer will accept whatever scenario unfolds ahead of the power unit homologation date.

The new F1 2026 power units are set to be homologated with the FIA on March 1, locking in the engine designs for the year ahead, but the date is fast-approaching alongside a furore that has emerged regarding compression ratios.

Toto Wolff: Mercedes ‘trusting’ Power Unit Advisory Committee

A change in compression ratios for this year has reduced from 18:1 to 16:1, with that requirement being measured with the power units at ambient temperature.

However, over the winter break, whispers emerged of letters of concern from several of the power unit manufacturers against an apparent compression ratio grey area being exploited by Red Bull Powertrains [RBPT] and Mercedes, sent to the FIA, with this noise ramping up as the homologation date has grown closer.

With RBPT believed to have now sided with the other three power unit manufacturers [PUMs], Honda, Audi, and Ferrari, the suggestion has long been that Mercedes has found a way to operate its power unit at a higher compression while on track at hotter temperatures, while conforming with the lower compression ratio when being measured.

This would conform with the exact wording of the full regulation, including the measurement requirement, but has emerged as a point of controversy for the other PUMs due to it allegedly exceeding the 16:1 ratio, ie. the first line of the regulation.

With the matter now being openly discussed by Mercedes team boss Toto Wolff amidst a series of meetings involving the Power Unit Advisory Committee, which is made up of the five PUMs and the FIA and F1, a resolution is being sought by way of “seeking alignment on the methodology of measurement of compression ratios at hot temperatures”.

A hot temperature compression ratio reading is not part of the regulations around which the power units have been designed and, should a rule change be introduced, it is theoretically possible that a power unit manufacturer could find itself unable to comply with the new requirements by the time of the homologation date.

For a rule change to occur, a supermajority at the PUAC level is required: four of the five PUMs, as well as the FIA and FOM, would have to agree.

As it stands, it’s understood that the four PUMs are in agreement, while the positions of the FIA and FOM are not yet clear. If the situation remains as it is until Australia, there is a distinct possibility of mass protests against the eight Mercedes-powered cars, while a rule change could theoretically leave Mercedes with an engine no longer able to conform with a tweaked ruleset just days or weeks away from the first Grand Prix.

Neither situation is particularly palatable, but Toto Wolff cut a calm figure as he sat down to address the situation with assembled media, including PlanetF1.com, at the first Bahrain test.

“The sport is full of surprises, so there is never a situation where you can say you’re sure about anything all along the process,” he said, when asked about whether the possibility of a supermajority forming against Mercedes power units has been assured by the FIA – the governing body’s position being critical to any potential vote.

“Obviously, when you design an engine, you’re keeping the FIA very close to the decisions you make and and that’s what we did, and we have had all the assurances that what we did was according to the rule.

“It’s not even like we’re talking about some massive performance gain, and that’s what it was.

“But I think all of our competitors got a little bit aggrieved and lobbied the FIA for a long time, and we trust in the governance of the Power Unit Advisory Committee. We’ll see how that goes.”

Revealing that running at a higher compression ratio than the prescriptive 16:1 while on track can offer gains in the region of “two to three” horsepower, Wolff ruled out the possibility that Mercedes could seek legal redress against the FIA should the rules be changed at this late stage.

“There is no such scenario that we would sue anyone,” he said.

“Formula 1, in my opinion, it’s more essential than ever that you know what the rules are, but engineering ingenuity is always respected and and that’s why we are always going to respect the governance of the sport, and if the governance of the sport decides to change the rules, against or for our position, we just have to get along with it.”

Given Mercedes’ communication with the FIA through its design, a rule change despite this transparency could be seen as surprising if the FIA was to join the four PUMs in agreement, but Wolff denied that he would feel misled if such a circumstance did emerge.

“I’ve been here for a while, and you’re being misled and you’re misleading all the time,” he said.

“So there is no such thing as surprises anymore. The wind can change suddenly.

“Bernie Ecclestone would say, ‘change of circumstance’. I said ‘A’ yesterday, but, today, my opinion is ‘B’, and that happens all the time.”

Will Mercedes’ engines be legal in Australia?

Given the difficulty in changing an engine design at this late stage in the game, a rule change potentially risks all Mercedes power units unable to conform with the updated regulations.

Should the manufacturer be unable to make necessary changes in time, the possibility then is that Mercedes-powered cars don’t participate until a revised solution is brought for homologation, or perhaps racing in Australia and then facing likely protests or disqualifications – the difficulty here being in a technical solution being devised in time to measure hot temperature compression ratios.

Asked whether a rule change would endanger Mercedes-powered cars’ participation in Melbourne for the season opener, Wolff didn’t directly confirm a scenario, but his answer suggests a contingency option may be in place.

“You develop an engine over a long time, and you have lead times,” he said.

“If you were to be told you can’t operate the engine in the way you have developed it, that could be quite damaging for the performance.

“If it becomes a regulation, you need to adhere to the regulation. And, if you can’t adhere to the regulation, then the FIA needs to come out with some kind of invention on how to adjust for that, and that’s unclear to us.”

PlanetF1.com understands that, at the final PUAC meeting ahead of the homologation date, the four other PUMs are set to propose a test mechanism for measuring compression ratios while running hot, ie. while on track. It’s on this solution that a vote is likely to be put to the PUAC, with that vote determining whether or not a supermajority is established.

“If that governance were to vote for an engine regulation change, you just have to take it on the chin,” Wolff said of that possibility.

“It is what it is. And obviously, in that case, it would be detrimental for all of the Mercedes-powered teams.

“I think that the lobbying from the other engine manufacturers has massively ramped up over the last few months.

“I mean, secret meetings, secret letters to the FIA where, obviously, there’s no such thing as secret in this sport, and that has brought it to to this situation.

“I’m a little bit more confused in the recent weeks about how it came to the point now that it suddenly became a topic.

“Because, until last Friday, I was given the impression that things wouldn’t change.”

With this answer suggesting that Mercedes has potentially been alerted to the possibility that the other four PUMs could be successful in securing the supermajority needed for a rule change, Wolff said that the Barcelona shakedown could have played a part in this.

“Everybody was a little bit too excited about the performance of the Mercedes-powered teams, and I think that our colleagues from the other brands have been carried away a little bit that this could be embarrassing, which I don’t think it is at all, but it’s okay,” he said.

“Let’s see how the tests pan out, and then God knows what the next black swan event happens to us.”

Acknowledging the importance of how FOM and the FIA vote on the matter, Wolff revealed that Mercedes has had the support of FIA President Mohammed Ben Sulayem.

“He’s someone who is interested a lot into his engines and his cars, and that’s why it was, from his perspective, clear what the regulation said and that the regulations were applied in the right way,” the Austrian explained.

“He’s the president of the FIA. He has all the powers in his hands to be part of the decision making. At the end of the day, it’s his call.

“You need the votes from the governing body, and you need the votes from the commercial rights holder, and, if they decided to to share an opinion and an agenda, then you’re screwed.”

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