Last Updated on February 2 2026, 7:52 am

The ‘private’ Formula One Barcelona test was awaited with huge anticipation as finally the biggest change in the sport’s technical design and power unit regulations manifest themselves in the all new cars for the coming F1 era. The test was not quite so private as the FIA anticipated with teams confirming their best lap times and distance covered each day at the Circuit de Catalunya.

Williams were conspicuous by their absence and after their best season in 2025 for over a decade, there were long faces back at base in Grove when the decision was taken to skip the first ore-season test. Reports emerged that the FW48 was as much as 20-30kg overweight and that the chassis had failed the FIA’s mandatory crash test.

Seven teams made day one of the pre-season outing, with both newbies Cadillac and Audi amongst the roster. Although McLaren had stated they intended to run on day two it was only Ferrari who made their debut on Tuesday as the mechanics of the papaya liveried car worked throughout the day behind the closed garage door.

 

 

 

Mercedes pound out the laps testing PU reliability

The world champions took to the track on Wednesday and finally late on day four Aston Martin managed to make it out, although for just five laps before Lance Stroll retired the car. Mercedes completed their three days on Thursday and set the benchmark for the rest of the field, accruing more than 500 laps – almost 8 Grand Prix distances – as the silver arrows pounded round and round in the hands of George Russell and Kimi Antonelli.

Interestingly, Mercedes admitted their intention for the test was to run long and hard with little or no car setup experiments. It was almost as though their purpose for the test was to stress their new powertrain to the limit, to see if there were any glitches in its design.

Prior to the Barcelona meeting, a number of reports had claimed that Mercedes have exploited a loophole in the FIA’s power unit regulations which restrict the compression ratio in the internal combustion engine to just 16.1, down from 18.1 in the old V6 turbo hybrids. The regulations state the compression ratio will be measured with the engine ‘cold’ and the car static.

Yet Mercedes High Performance Powertrains is said to have found a loophole in the new rules, which means by using clever metallurgical elements, when the car is on track and the engine is hot, the compression ratio rises to around 18.1. Ferrari, Honda and Audi all demanded a response From F1’s governing body, although in a pre-test pow wow, Nicolas Tombazis appeared to rule out any further action against the silver arrows.

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Newey predicts combustion engine domination

Further, the way the teams go about their car and PU designs in the modern F1 era, is by submitting detailed drawings along the way for the FIA to approve. It appears the Mercedes PU has at each step of its development received the appropriate approval from the sport’s governing body and can therefore not be protested by its competitors.

Yet Ferrari have pushed back against the decision blaming that the FIA’s head of day to day F1 affairs does not understand the severity of the Mercedes’ potential regulation breach and will press the matter come the opening race weekend of the season in Melbourne.

The seriousness of any such advantage was outlined by Aston Martin’s Adrian Newey at the 2025 Autosport January awards. “There has to be a chance that one manufacturer will come out well on top and it will become a power unit-dominated regulation, at least to start with. And there’s a chance that if it’s on the combustion engine side of it, that somebody comes up with a dominant combustion engine, that will last through the length of the formula, because the way the regulations are written it’s quite difficult for people who are behind to catch up. If it’s on the electrical side, then there’s much more ability to catch up if you’re behind.”

Italian based publication Motorsport Italia reports today that the FIA have been offered three options to ensure Mercedes is not gaining an unfair advantage with their new internal combustion engine. The first is based on the FIA’s catch up mechanism which allows manufacturers who have a significant power deficit to the lead engine the ability to redesign their 2026 PU’s.

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FIA’s 3 options to reign in Mercedes

Yet the incremental lead times on engine development when compared to chassis and aerodynamic components means it could be late in the season before the deficit is nullified. A power unit using a greater compression, will also use more fuel and so the second option for the FIA would be to impose a flow restriction on the Petronus manufacturers fuel.

The previous power unit regulations did restrict the actual fuel flow, as Red Bull found to their dismay first time out in 2014. Both cars were disqualified at the season opener in Melbourne due to their fuel flow rates being deemed to be higher than the limit allowed.

The problem with the Mercedes ‘trick’ is that whilst it would be in breach of the FIA regulations, it is the test which us unable to prove the case. So a final option for the FIA would be to request Mercedes sign a waiver explicitly stating their powertrain does not breach any of the 2026 technical rules.

Whilst this approach may appear rather insipid, the implications of Mercedes being caught lying from a future FIA investigation are massive. The team and/or both drivers could be disqualified from each of the races in which they have taken part this season – or even as McLaren suffered in 2008, chucked out of the entire 2026 F1 championship.

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Red Bull now join others in questioning Mercedes PU

Of note is the fact that Red Bull have now joined the calls of Audi, Ferrari and Honda for the FIA to guarantee the legality of the Mercedes power unit. The consequence of failing to do so may well lead to a protest when the season begins in Australia. Red Bull were initially believed to have recruited engineers from Brackley who had revealed the Mercedes loophole and that Red Bull Power Trains had copied the design, but this has been vehemently refuted.

Whilst Mercedes may well have provided the FIA with detailed drawings and specifications along the path of its PU development, this does not guarantee the scrutineers from F1’s governing body have missed the trick Mercedes were developing before their very eyes.

Whilst the FIA cannot change the technical regulations without unanimous agreement – which Mercedes will not give – they can change their testing procedures and a live fuel flow measure would reveal any discrepancies in compression rates on track and when the car is stationary in the paddock.

The matter is almost certain to be protested in Melbourne and F1’s all new era will start with a row over cheating once again.

 

 

 

 

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