You know this is another of these stories. We were told compression ratio is something that we were illegal, which is total bullshit. Utter bullshit, and now the next story comes up that our fuel is illegal? I don't know where that comes from and it starts spinning again.
This is measured at ambient temperature, though, not while the engine is running. A running engine is hotter—much hotter—than one sitting at ambient, and as metals heat up, they expand. The engines have very short throws, so it doesn't take much expansion to increase the compression ratio by reducing the distance between the piston and cylinder head at the top of its travel.
