Honda secretly introduced its second ADUO upgrade at the Spanish Grand Prix to fix turbocharger issues.

Honda Racing Corporation president Koji Watanabe revealed that Honda actually used both of its ADUO development tokens this season, introducing the second upgrade as early as the Spanish Grand Prix. The upgrade focused on improving the turbocharger to address drivability issues with the first ADUO specification introduced in the Netherlands.

The Spec 2 power unit debuted at Zandvoort with some drivability problems, prompting Honda to develop an improved turbocharger that was fitted to Lance Stroll's car in Spain. Fernando Alonso received the upgraded turbo at the Azerbaijan Grand Prix. The staggered introduction resulted from Honda working on turbo lag solutions in parallel with the main upgrade package.

Watanabe explained that Honda is still not extracting the full potential of its power unit despite using both ADUO opportunities. The company will focus on developments that do not involve hardware changes for the remainder of 2026, while working on improvements for future seasons. Honda previously used reliability development techniques during its Red Bull partnership to gradually raise operating limits.