Fernando Alonso will take a 35-place grid penalty for the Italian Grand Prix after Honda chose to test its latest upgrade during first practice in the Spaniard's McLaren.
Honda had initially hoped to run their full upgrade, Spec 4, but has now chosen to run an interim version dubbed Spec 3.7, which will mean an entirely new power unit, consisting of a seventh ICE and MGU-K, a ninth MGU-H and Turbocharger, a sixth Energy Store and a fifth Control Electronics, being fitted.
Alonso will then switch back to the Spec 3.5 power unit he ran during the Belgian GP weekend for FP2, after Honda found no issues with it, despite Alonso retiring his car amid sensor problems.
The switch gives Alonso a brand new penalty-free power unit for the Singapore weekend – where McLaren expects to be more competitive – whilst giving Honda some practice running data to work with.
Team-mate Stoffel Vandoorne will retain the Spec 3.5 power unit that he used across Saturday and Sunday at Spa-Francorchamps for the entire Monza weekend.