Why McLaren can't extract as much as Mercedes from its F1 power unit

Two races into the 2026 Formula 1 season, McLaren finds itself in the uncomfortable position of sharing the power unit with the team currently leading the championship, but having been nowhere near its supplier.

The numbers have been stark for the Woking team, and by its own admission, the gap to Mercedes is not exclusively down to the power unit, but because of the car around it.

In Melbourne, McLaren was 0.85 seconds per lap off the pace of the Mercedes works team, and team boss Andrea Stella attributed part of the gap to a lack of understanding about the power unit.

He acknowledged that conversations with Mercedes about obtaining more complete power unit information had been ongoing for weeks, stretching back through pre-season testing.

“Even during testing, we’d go out on the track, start the car, look at the data, and say, ‘Oh, that’s what we have. Okay, now we need to react,’” Stella said.

“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.

It was, Stella noted, the first time since becoming a Mercedes customer that the team felt it was on the back foot even in its ability to predict how the car would behave.

By Shanghai, the tone had shifted. Mercedes had provided additional support, Stella was notably more conciliatory, and the gap to the works team had narrowed to 0.45 seconds.

The improvement had come in part from a better understanding of how to deploy and harvest energy with the Mercedes power unit, developed with direct input from the manufacturer since Australia.

Most of the gain between the two races was down to that growing fluency. The rest, the deficit that remained after all the deployment learning had been applied, was the car itself.

That distinction matters because it reframes the problem, as McLaren does not have an engine issue. It has an aerodynamic one, and under the 2026 regulations, those two things are more tightly connected than before.

In previous regulations, a car lacking rear load paid a straightforward lap time penalty: less grip, less speed through corners, slower overall.

In 2026, the consequences extend beyond that.

Veteran F1 journalist Mark Hughes, speaking on the Motor Sport F1 Show podcast, offered the clearest explanation of why insufficient downforce is particularly damaging now

“You cannot harvest the power as aggressively if you don’t have as much downforce at the rear of the car,” Hughes explained. “You can harvest much more effectively with a car with more rear downforce.”

That means that a car that is aerodynamically behind is not just slower in the conventional sense, but also less capable of regenerating enough energy, which means it arrives at the next deployment phase with less charge than a rival running a more planted car.

That disadvantage compounds itself after every lap.

This is where McLaren currently sits ahead of the Japanese GP. While its car is competitive enough to run near the front on raw pace, it’s not yet in the same class as the Mercedes in terms of pure rear load.

Hughes identifies two plausible explanations for how McLaren ended up in its current situation, and suspects the truth involves elements of both.