What the BMW S38 Is
The BMW S38 is a naturally aspirated 3.5-liter inline-six built by BMW Motorsport, introduced in 1986 as the beating heart of the first M5. Producing roughly 340 horsepower in its early European guise, it traced its lineage directly to the M88 competition engine used in the M1 supercar. This gave the S38 a genuine motorsport pedigree that set it apart from ordinary six-cylinder BMWs of the era and made it the definitive M-series straight-six of the late 1980s.
Part of the S38 family, this engine established the template that later high-revving M motors would follow. To see how it fits into BMW's broader lineage of performance powerplants, explore the BMW DNA overview.
Architecture and Engineering
The S38 is a classic front-mounted, longitudinal inline-six with an iron block and an aluminum cylinder head. Key engineering hallmarks include:
- Four valves per cylinder operated by twin overhead camshafts, a direct descendant of the M88 design.
- Individual throttle bodies — one per cylinder — giving crisp throttle response and that distinctive M-engine intake character.
- A displacement of 3.5 liters in its initial form, with later evolutions growing in capacity and output.
- A strong, over-built bottom end designed to handle sustained high-rpm operation.
This combination of race-derived breathing and robust internals gave the S38 its signature blend of tractable low-end torque and an exhilarating top-end pull. It sits alongside other legendary M fours and sixes such as the S14 four-cylinder and the later S50 straight-six as a cornerstone of M division engineering.
Which BMWs Used It
The S38 is best known as the powerplant of the first-generation M5 (E28), and it went on to power subsequent M5 generations as well as the M6 and 6 Series M coupe in various markets. Because M engines and applications varied by region and model year, decoding a specific car's build details is the surest way to confirm what lies under the hood — use the VIN decoder to verify your engine and specification.
Reliability and Ownership Notes
The S38 is regarded as a durable, over-engineered motor when properly maintained, but ownership demands respect for its age and complexity. Prospective owners should note:
- Valve adjustments and timing chain condition require periodic attention on these mechanical, high-strung engines.
- The individual throttle bodies benefit from careful synchronization to run smoothly.
- Cooling system components and rubber intake pieces age with time and are common refresh items.
Parts and specialist knowledge remain available thanks to the engine's enthusiast following. For those cross-shopping later M sixes, the S54 represents a modern evolution of the same high-revving philosophy the S38 pioneered.