Honda director Toyoharu Tanabe has admitted his surprise to see both Mercedes and Ferrari's upgraded power units suffer failures at the Belgian Grand Prix.
Honda's spec-4 engine got through Spa-Francorchamps with no issues, as Alexander Albon on his Red Bull debut, and Daniil Kvyat both fought into the points after starting at the back of the grid.
It was not so smooth for Mercedes, though, with Sergio Perez suffering an issue towards the end of Friday practice, which forced him to revert to an older spec engine for the race.
Williams' Robert Kubica then suffered a spectacular blowout during qualifying, while Antonio Giovinazzi suffered an issue in the same segment in Spa, giving Ferrari a headache as they plan to introduce the upgrade in their home race in Monza this weekend.
Tanabe told Motorsport.com: "I'm surprised, for two reasons. One, their reliability showed in the past, and also this year. We can only use three engines per year, so they must run more than 5,000km.
"They have a lot of experience of how to guarantee the mileage and the reliability using dyno endurance tests.
"The new spec, of course, passed that durability test in the factory, then the engine came [to Spa] and had trouble. That is one question and also [why I am] surprised.
"The other is quality control: they supply two or three teams for a long time, they know how to control the quality, how to check it before they ship [to races]."
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