Here's why Mercedes is delaying Kimi Antonelli’s ADUO engine upgrade

Antonelli accepts a Monza penalty without Mercedes’ latest upgrade

Mercedes has confirmed that Kimi Antonelli will not use the power-unit upgrade available to the team under Formula 1’s Additional Development and Upgrade Opportunities scheme at this weekend’s Italian Grand Prix.

The championship leader will instead take a completely new engine, exceeding his power-unit allowance for the 2026 season and triggering a start from the back of the grid at his home race. Mercedes has selected Monza because its layout is considered one of the more favourable venues for recovering positions after a grid penalty.

The decision comes with 11 rounds still remaining on the calendar, although the eventual status of the Qatar and Abu Dhabi races remains pending. That leaves Mercedes assessing how much mileage its power units must cover and where future penalties would carry the smallest competitive cost. The situation has already prompted wider discussion around the team’s engine strategy, including Mercedes’ separate decision on George Russell’s engine penalty.

The upgrade will wait until October

The new unit Antonelli receives at Monza will not include Mercedes’ permitted ADUO upgrade. Its introduction is scheduled for the American leg of the championship in October, with Austin or Mexico City identified as the possible debut venues.

That timing means Antonelli and team-mate George Russell are expected to use six power units across the full championship, leaving both drivers exposed to further grid drops later in the season. For Antonelli, however, the immediate issue is not simply the timing of the upgrade. It is the size of the engine pool still available to him.

Reliability has reduced Antonelli’s options

Reliability problems, failures and other terminal issues have reduced the number of usable components in Antonelli’s pool, making a new unit necessary before Mercedes’ updated power unit is ready. Waiting for the October specification was therefore not a straightforward alternative.

Russell has used the same number of components as Antonelli but is in a stronger position because fewer terminal failures have reduced his available pool. The contrast explains why Mercedes can manage the two drivers differently, even though both are expected to reach six power units during the season.

For Antonelli, Monza is consequently a calculated compromise: accept the penalty at a circuit where recovery is possible, preserve the ADUO upgrade for October and protect the remaining engine allocation as the championship enters its final phase.