I'm not necessarily talking about the "engine" vs "power unit" debate with the new energy recovery systems and whatnot, though that is part of the problem. I'm more interested in the realm of the Grandfathers Axe / Ship of Theseus Paradox.

If I replace a blown MGU-K seal, is it the same engine? What about a rod bearing? The block? An oil pump?

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    In case it's helpful, the FIA seems to publish a document before each race indicating the how many power unit elements have been used to date by each driver. For example, in the 2019 season documents you'll find for each race a "PU elements used per driver up to now" document.
    – cjs
    Oct 26, 2021 at 7:57

1 Answer 1


From the Formula 1 website:

Unless he drives for more than one team, each driver may use no more than four power units during a championship season.

The power unit is deemed to consist of six separate elements, of which five of each are available to a driver during the season before they are penalised. The elements are [various defined items].

Each driver is permitted to use only four of each of the above six elements during a championship season and any combination of them may be fitted to a car at any one time. Should a driver use more than four of any of the six power unit elements during the course of a season, a grid penalty will be imposed.

In simpler language: an "engine" consists of six different "parts". Each driver may replace each part four times before receiving a penalty. They are further limited so that they cannot replace all parts four times.

Thus for the purposes of the engine replacement limit, the "engine" is counted as one complete set of the engine components available. When you've used one complete set of components, you've used one engine. When you've used four complete sets of components, regardless of the order in which you replaced any specific components, you've used four engines and won't be allowed any more.

In terms of the Racecar of Theseus, it's all still the same engine until you've replaced everything at least once - then for the purpose of counting engines, that's when it becomes a new one!

  • Thank you for the link and the explanation! It's interesting that they place seals on the major components.
    – plast1k
    Jun 4, 2015 at 14:05

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