Alonso and Stroll retire at Mexico Grand Prix due to power unit failure

The double retirement

Lance Stroll and Fernando Alonso both retired within six laps of the Mexico Grand Prix start because abnormal pressure levels in the power unit systems forced them out. Alonso stopped his car on lap five after a pit stop on lap three, while Stroll parked his car on lap six to avoid damaging the battery. This failure followed a qualifying session where Alonso encountered "abnormal signals on the water systems" that relegated him to 17th on the grid. The team’s weekend saw significant volatility after the AMR26s completed 144 laps during practice sessions without failure, yet the cars failed to last even a fraction of that distance during the competitive sessions. I find the loss of pace disappointing after Alonso finished FP2 in P12, only 0.769s behind Charles Leclerc. Alonso showed impressive pace before the failure, as his quickest three sectors on Sunday put him nearly as quick as Williams’ Carlos Sainz, despite Alonso carrying a heavy fuel load. Both cars finished in Q1 during Saturday’s qualifying, four tenths down on the Q2 cut-off time.

Honda’s altitude error

Honda trackside general manager and chief engineer Shintaro Orihara admitted the Japanese manufacturer underestimated the cooling demands of the high-altitude Autodromo Hermanos Rodriguez. The track sits 2,285 meters above sea level. Air density remains 20 percent lower than at sea level, forcing turbochargers to work harder to compress oxygen. Orihara explained that the ERS cooling circuit faced heavier stress than the team anticipated. The new, simpler power units no longer have the MGU-H device that previously supported the turbo to reduce lag, which adds difficulty in the thin Mexican air. Because the power unit lacks this device, the team must find new solutions. Orihara pointed out that in previous years the MGU-H supported the turbo to reduce lag, but the 2026 power units lack that component. This combination of thin air and simplified engine architecture caused the cooling circuit to fail under pressure. Honda intends to use the gathered data to prepare for 2027.

Team frustration and Newey

Aston Martin chief trackside officer Mike Krack noted the team struggles to maintain motivation following a difficult start to the 2026 campaign. Krack stated that the team saw better results after introducing upgrades and the ADUO, but the current season brings more reliability trouble. He also mentioned that in Texas, the team faced different issues with incidents. Alonso, who faces his seventh retirement this season, called the result "a frustrating end to the day." Alonso, who had already experienced intense frustration after qualifying on Saturday due to a suspected ERS-related water pressure issue, faced further disappointment when the same MGU-K problem reoccurred during the race to force his retirement. Even with the DNF, Alonso insisted that his preparation remains focused on performing at his best behind the wheel. He added that he felt the challenge with the altitude was probably underestimated by the power unit. He described the weekend as a failed "moment of truth" test. Adrian Newey watched the race from the pit lane, where he studied the Ferrari SF-26. Newey joined Aston Martin in 2024 following his departure from Red Bull in 2025. Krack noted that if the team gets the driveability under control, they can be competitive in low-speed corners like the stadium section with Turns 4, 5, and 6. The reliability issues follow a season where severe vibration issues damaged battery packs and limited pre-season running, alongside engine struggles with straight-line power.