Traditionally, V8 engines in big sedans and trucks use a cross plane crankshaft. This setup is known for its signature deep sound and, more importantly, its buttery smooth performance. Cross plane V8s naturally cancel out most vibrations with the help of crankshaft counterweights, making them perfect for quiet, refined cruising. In contrast, flat plane V8s are built for performance. They are lighter, rev more freely, and are common in high end sports cars because of their responsiveness and willingness to climb the rev range quickly.

Here’s the catch: flat plane V8s vibrate much more than cross plane designs. They buzz and rattle, especially at certain engine speeds, which is the exact opposite of what most S-Class owners expect from their flagship sedan. Usually, luxury car makers avoid these engines unless they have a very good reason, or some clever engineering tricks—to keep things feeling smooth and comfortable.

So, why go against decades of tradition? Mercedes hasn’t shared all the details, but it’s likely about both future performance and the need for manufacturing flexibility as new models roll out. A flat plane V8 is simpler to build and is favored in supercars for a reason: it’s responsive and rev happy. Maybe Mercedes wants to blend that sporty edge with luxury, or maybe it’s preparing for a world where engines need to share more parts across different models.

The big question is how Mercedes will tame the inherent roughness of this engine. The company claims it has achieved “exceptional smoothness,” so there are probably new balance shafts, innovative engine mounts, or other tech below the surface to keep the S-Class experience intact. If they succeed, the S-Class could change what we expect from big, powerful sedans, and maybe even influence other models in the lineup.