Mercedes has chosen not to introduce its new ADUO-spec engine at Interlagos. The team has kept the token in reserve for Las Vegas, the next race after Brazil, where overtaking is easier and any grid penalty for Russell would be less costly.

The decision lands on the eve of a critical weekend. Mercedes leads Ferrari by 126 points in the constructors’ standings after round 19 in Mexico City, with sprint points on offer in São Paulo on Saturday and the main race on Sunday. The title is not mathematically settled, and every weekend from here shapes how close the team can bring it to the line.

Why the upgrade keeps slipping

The ADUO engine was originally earmarked for the United States Grand Prix in Austin, then penciled in for Mexico, then flagged as a likely Brazil debut by outlets reporting on the postponement in late October. None of those windows held.

The team’s position has been consistent: the upgrade is only going into a car when the dyno numbers confirm a real step forward. Rushing a token Mercedes only has one of in 2026 would be worse than losing another race weekend to the current specification.

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Grande Prêmio reported that Mercedes has also been weighing which circuit offers the best chance to recover from the grid drop attached to a fresh power unit. Interlagos is a strong overtaking venue, but Las Vegas, with its long straights and DRS zones, is widely seen as friendlier for a car starting toward the back.

What ADUO actually gives Mercedes

ADUO, short for Additional Development and Upgrade Opportunities, is the FIA mechanism designed to stop one manufacturer running away with the new 2026 engine formula by handing extra development slots to teams measured a set distance behind the strongest combustion engine.

Red Bull, in its first season as a full power unit manufacturer, was judged the benchmark. Mercedes was assessed as more than two per cent adrift of that reference, and the FIA granted the team one extra upgrade token for 2026 and another for 2027, plus a $3 million cost cap allowance and 70 additional hours of bench testing.

The 2026 token has to be used before the season ends or it is forfeited. That, more than anything, sets the ceiling on how long Mercedes can keep delaying.

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Russell’s penalty is already coming

George Russell has been tied to this decision for weeks. After a power unit failure at the Malaysian Grand Prix, Mercedes fit a new engine for Russell in Singapore, sending him to the back of the grid, as PlanetF1 reported at the time.

The Singapore engine was not the ADUO upgrade. That is still ahead of him, and it will bring another penalty. Russell had made clear in media interviews, cited by PlanetF1, that the plan was always to time the grid drop with the arrival of the new specification.

“We’re waiting to take my penalty with the ADUO upgrade; otherwise, if I took it there, I’d have to take it again, so it made zero sense for me,” Russell said.

With Brazil now ruled out, that wait extends into Las Vegas. Mercedes has not formally confirmed Las Vegas as the debut, but it is the next viable opportunity on the calendar and the one the team’s own strategic logic points to.

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What to watch at Interlagos

For this weekend, Mercedes runs the current engine in both cars. Russell starts from his natural grid slot, and the team’s margin over Ferrari is defended with the specification that built the 126-point cushion in the first place. The engine story picks up again in Nevada.

Qualifying at Interlagos is scheduled for Saturday, with the race on Sunday, 8 November.

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