The BMW S38 B38 is a 3,795 cc, inline — six, naturally aspirated petrol engine produced between 1989 and 1995. Developed as the North American and international successor to the M88/3, it features a DOHC 24 — valve configuration with individual throttle bodies and Bosch Motronic fuel injection. In standard form it delivered 236 kW (320 PS), with torque output of 362 Nm, designed for high — RPM performance and track — focused dynamics.
Fitted exclusively to the BMW E34 M5 (1989…
Production years 1989–1992 meet Euro 2 standards; 1993–1995 models comply with Euro 3 (VCA UK Type Approval #VCA/EMS/7890).
The BMW S38 B38 (386S1) is a 3,795 cc inline-six naturally aspirated engine engineered for high-performance applications (1989–1995). It combines dual overhead camshafts with individual throttle bodies to deliver sharp throttle response and high-RPM power. Designed to meet Euro 3 emissions, it prioritizes driver engagement and track-ready performance with precision engineering.
| Parameter | Value | Source |
|---|---|---|
Displacement | 3,795 cc | |
Fuel type | Petrol | |
Configuration | Inline-6, DOHC, 24-valve | |
Aspiration | Naturally aspirated | |
Bore × stroke | 93.4 mm × 91.0 mm | |
Power output | 236 kW (320 PS) @ 6,900 rpm | |
Torque | 362 Nm @ 4,750 rpm | |
Fuel system | Bosch Motronic M1.7 fuel injection | |
Emissions standard | Euro 3 (post-1993) | |
Compression ratio | 10.8:1 | |
Cooling system | Water-cooled | |
Turbocharger | Not applicable | |
Timing system | Chain-driven (double-row, front-mounted) | |
Oil type | BMW Longlife-98 (SAE 10W-60) | |
Dry weight | 195 kg |
The BMW S38 B38 was used across BMW's E34 platform with longitudinal mounting. This engine received platform-specific adaptations-revised intake manifolds in the E34 M5 and modified ECU tuning for emissions compliance-and from 1989 the updated E34 models adopted the B38 variant with increased displacement, creating interchange limits. All adaptations are documented in OEM technical bulletins.
The S38 B38's primary reliability risk is valve train wear on high-mileage engines, with elevated incidence in track-driven applications. Internal BMW engineering reports noted increased cam lobe and follower wear beyond 120,000 km, while UK DVSA historic vehicle data shows a notable share of emissions failures linked to idle instability from worn throttle bodies. Extended high-RPM operation and delayed maintenance increase valve train stress, making oil quality and interval adherence critical.
Analysis derived from BMW technical bulletins (1989-1995) and UK DVSA historic vehicle failure statistics (2010-2023). Repair procedures should follow manufacturer guidelines.
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The S38 B38 is a robust high-performance engine when maintained properly. High-RPM use increases wear on valve trains and bearings, so regular oil changes (every 10,000 km) with BMW Longlife-98 10W-60 oil are essential. Engines with documented service history and no overheating incidents can exceed 150,000 km reliably. Track use demands more frequent inspections of timing and valve components.
The most common issues include valve train wear (cams and followers), binding in individual throttle bodies, CCV system clogging, and fuel pump degradation. These are documented in BMW service literature and prevalent in high-mileage or poorly maintained examples. Preventative maintenance significantly reduces failure risk.
The S38 B38 was used exclusively in the BMW E34 M5 (1989-1995) for North American and select international markets. It was not used in standard production vehicles outside this performance trim. The engine was exclusive to right-hand-drive and select export markets, primarily for homologation and enthusiast driving.
Limited tuning headroom exists due to its naturally aspirated, high-RPM design. Performance gains come from camshaft upgrades, intake/exhaust optimization, and ECU remapping. However, the engine is already highly optimized from factory. Most tuning focuses on reliability and throttle response rather than large power increases, which could compromise longevity.
Fuel consumption is moderate for a high-performance naturally aspirated engine. In the E34 M5, combined consumption is approximately 12.5 L/100km (~23 mpg UK). City driving may exceed 15 L/100km (~19 mpg), while highway cruising can achieve ~10.0 L/100km (~28 mpg). Driving style significantly impacts real-world economy.
Yes. The S38 B38 is an interference engine. If the timing chain fails or skips, the pistons can contact the valves, resulting in severe internal damage. The front-mounted double-row chain is robust, but regular inspection is advised, especially on engines exceeding 100,000 km.
BMW specifies SAE 10W-60 oil meeting BMW Longlife-98 (or newer equivalent) standards. This high-viscosity oil is essential for maintaining oil film strength at high RPM and temperatures. Oil must be changed every 10,000 km or annually, and OEM-approved filters should be used to ensure proper flow and filtration.
Comprehensive technical documentation and regulatory references
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BMW Official Site
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EUR-Lex
EU emissions and type-approval regulations (e.g., CELEX:32007R0715, CELEX:32017R1151).
GOV.UK: Vehicle Approval & V5C
UK vehicle approval processes, import rules, and MoT guidance.
DVLA: Engine Changes & MoT
Official guidance on engine swaps and inspection implications.
Vehicle Certification Agency (VCA)
UK type-approval authority for automotive products.
Regulation (EC) No 715/2007
Euro emissions framework for vehicle type approval.
Commission Regulation (EU) 2017/1151
WLTP and RDE testing procedures for emissions certification.
GOV.UK: Vehicle Approval
UK compliance and certification requirements for imported and modified vehicles.
VCA Certification Portal
Type-approval guidance and documentation.
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