McLaren team principal Andrea Stella has revealed his discontent at a lack of engine "information" being provided by Mercedes after a huge gap between supplier and customer became apparent during Formula 1's season-opening Australian Grand Prix.
Reigning constructors' champions McLaren were well off the pace of Mercedes, who claimed a one-two as George Russell led Kimi Antonelli home for the Silver Arrows in Melbourne.
Reigning world champion Lando Norris finished 51 seconds behind Russell in fifth, while his team-mate Oscar Piastri was unable to start the race after a bizarre crash on his way to the grid.
Mercedes were expected to have an advantage as a works team manufacturing their own engine, but Stella admitted McLaren are surprised by the extent of the advantage their supplier appears to have in terms of energy deployment with F1's all new cars for 2026 following a major regulation change.
Stella said: "The discussion with HPP (Mercedes High Performance Powertrains) about having more information has been going on for weeks because, even in testing, we were pretty much going on track, run the car, look at the data, 'oh, that's what we have. Good, now we react to what we have'.
"That's not how you work in Formula 1. In Formula 1, what happens on track, you simulate. You know what is happening, you know what you are programming, you know how the car is going to behave.
"So, you also have your plans as to how you evolve it that you have figured out before because you know what you are expecting from the car.
"So, I have to say, since we are a customer team [of Mercedes], this is the first time that we feel we are on the back foot even when it comes to the ability to predict how the car will behave and the ability to anticipate how we can improve the car."
Following the race Stella was asked about James Vowles, the team principal of fellow Mercedes' customer Williams, saying that his team had been "caught off guard" by their supplier's efficiency in terms of deployment.
The Italian, whose team romped to the title last year, said he believed there was "low hanging fruit" for McLaren to take advantage of but admitted he was not sure that would be enough to close the gap to Mercedes.
"I don't know about Williams," Stella said. "Honestly, I can say that we spent a lot of time looking at several overlays, not only with HPP teams, in particular Mercedes, but also to other competitors.
"And definitely, the result of this analysis seemed to direct to the fact that we have work to do as a team in collaboration with our HPP engineers. We have work to do to exploit the potential of the power unit, which, once I see the potential that HPP is extracting, looks like there's more that is available.
"Now, it's not obvious how you do that. For us, we are in a journey of knowledge, certainly, a journey that is earlier than the works team.
"The works team and HPP will have worked together for a long time. So, they will have collaborated, talked about how to use the power unit. That's fair enough, but we'll definitely intensify the collaboration with HPP because our understanding is that there is some low hanging fruit that we should be able to cash in.
"When it comes to, is this all that is available and that we are underexploiting? I am not sure.
"I think we will need some more analysis to understand whether this is only about parameters that we can control, or drivers' input that we can control, or there are some other factors, more systemic, that not necessarily a customer team can control."
Mercedes chief Toto Wolff warned that an engine supplier cannot "make everybody happy" when he was asked potential concern from his team's customers.
The Silver Arrows appeared to go to great lengths to hide their performance during pre-season and even the first day of practice in Australia, before unleashing stunning pace in Saturday's final warm-up session and claiming a front-row lockout in qualifying.
"It's clear when you roll out new regulations, there's so much to learn," Wolff said.
"Whether you have a customer that's on your gearbox or suspension, and in the same way on the power units, the development slope is very steep.
"You can never deploy things to make everybody happy. But I think most important is we're trying to provide a good service."
McLaren were further disadvantaged by Piastri's devastating crash ahead of his home race, which saw him miss out on the opportunity to start a place ahead of Norris in fifth on the grid.
The Australian was caught out by a spike in power from his power unit, which combined with the cold state of his tyres and him running over a kerb to send the McLaren into the barriers.
Stella is backing Piastri, who is known for his level-headed demeanour, to bounce back at next weekend's Chinese Grand Prix.
"It was very unfortunate, definitely a tough moment for him in front of the Australian crowd," Stella said.
"But Oscar is a very tough guy mentally. He will use all this to get even more concentrated and determined, starting from China. So, we will make sure that we all face this in a united way. We are a team in any situation that may involve anybody on our team.
"When it comes to the circumstances, what we observe, I think, is fundamentally three factors. The cold tyres, therefore, when the wheelspin starts, it starts in a very sudden way. This compounds with the being on a kerb. It's a kerb that he has used pretty much every single lap. Kerbs don't make this easier, though, when the tyres are cold.
"And this further compounds with an element that doesn't make it easier again, which is the fact that with these oscillations and following the shift, there's an extra torque that when we look at the behaviour of the power unit, it's sort of expected to happen like that, but it is not something that you would do unless it's, which I understand is the case, sort of some requirements that you need to meet in terms of how you deploy your torque.
"In testing, we might have seen some similar circumstances, but we didn't have the combination of cold tyres and the kerb which aggravated the fact that you may have these inconsistencies with torque deployment in grip-limited phases."
Formula 1 heads to Shanghai for the first Sprint weekend of the 2026 season at the Chinese Grand Prix from this Friday, live on Your Site F1.
