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Mercedes-Benz M256 specs: 3.0L (183 ci) 6-cylinder, 83 x 92.4 mm (3.2677 x 3.6378 in) bore and stroke, 10.5:1 compression. Rated 362-429 hp, 2019–2026.
The Mercedes-Benz M256 is undersquare — the 3.6378" stroke exceeds the 3.2677" bore by 10.2% — a layout that trades peak RPM for leverage and torque low in the range. The 3.6378" stroke puts mean piston speed at 4,000 ft/min around 6,600 RPM, which is where a production bottom end is generally considered at its limit. Each of the 6 cylinders displaces 30.5 ci (500 cc).
10.5:1 is in the range that usually runs on pump premium.
It is one of 17 engines in the Mercedes-Benz 183ci family, all of them 183 ci — the differences between them are in compression, heads and rating, not displacement. 11 factory variants share these dimensions, rated from 362 to 429 hp across 2019–2026.
| Displacement | 183 ci / 3 L |
|---|---|
| Bore | 3.2677" |
| Stroke | 3.6378" |
| Cylinders | 6 |
| Configuration | I6 |
| Compression ratio | 10.5:1 * |
| Bore/stroke ratio | 0.898 |
* Compression ratio from a single source; not yet cross-verified.
| Fuel type | gas |
|---|---|
| Advertised HP | 362–429 hp |
| Years | 2019–2026 |
| Bore/stroke character | 0.898 — undersquare — stroke exceeds bore, which favours low-end torque |
|---|---|
| Mean piston speed at 6,000 RPM | 3,638 ft/min — in the range typical of performance street engines |
| Displacement per cylinder | 30.5 ci |
| Static compression | 10.5:1 — in the range that usually runs on pump premium |
Each link opens the calculator with this engine's specs already filled in.
These records share identical bore, stroke, displacement and compression. They differ by model year and factory power rating.
| Year | Advertised HP | Code |
|---|---|---|
| 2019 | 429 hp | M256 |
| 2020 | 429 hp | M256 |
| 2021 | 362 hp | M256 |
| 2021 | 429 hp | M256 |
| 2022 | 362 hp | M256 |
| 2022 | 429 hp | M256 |
| 2023 | 362 hp | M256 |
| 2023 | 429 hp | M256 |
| 2024 | — | M256 |
| 2025 | — | M256 |
| 2026 | — | M256 |
3 factory vehicles, 2019–2026. Each year opens that model's engine table.