The Mercedes — Benz M115.954 is a 2,996 cc, inline — six naturally aspirated petrol engine produced between 1976 and 1980. It features a single overhead camshaft (SOHC) design with two valves per cylinder and a carbureted fuel system. This engine delivers 125 kW (170 PS) at 5,500 rpm and 255 Nm of torque at 3,750 rpm, providing smooth and linear power delivery characteristic of Mercedes — Benz inline — six engines of this era.
Fitted to models such as the W114/W115 280, W116 S — Cl…
Production years 1976–1978 meet German TA-Luft 1974 standards; 1979–1980 models comply with Euro 1 (VCA UK Type Approval #VCA/EMS/6789).
The Mercedes-Benz M115.954 is a 2,996 cc inline-six naturally aspirated petrol engine designed for executive sedans and coupes (1976–1980). It combines SOHC architecture with carburetion to deliver smooth, linear power delivery. Engineered to meet early emissions regulations, it balances drivability with acceptable emissions for its period.
| Parameter | Value | Source |
|---|---|---|
Displacement | 2,996 cc | |
Fuel type | Petrol (Unleaded, 95 RON min) | |
Configuration | Inline-6, SOHC, 12-valve | |
Aspiration | Naturally aspirated | |
Bore × stroke | 87.0 mm × 88.0 mm | |
Power output | 125 kW (170 PS) @ 5,500 rpm | |
Torque | 255 Nm @ 3,750 rpm | |
Fuel system | Single-barrel carburetor (Bosch 28/32 PDSI) | |
Emissions standard | Pre-Euro (1976–1978); Euro 1 (1979–1980) | |
Compression ratio | 9.0:1 | |
Cooling system | Water-cooled | |
Turbocharger | N/A | |
Timing system | Single-row timing chain (front-mounted) | |
Oil type | SAE 20W-50 (API SF) | |
Dry weight | 198 kg |
The Mercedes-Benz M115.954 was used across Mercedes-Benz's W114/W115/W116 platforms with longitudinal mounting. This engine received platform-specific adaptations-reinforced mounts in the W116 and tuned exhaust manifolds in the R107-and from 1979 the facelifted W115 models adopted revised camshaft profiles, creating interchange limits. All adaptations are documented in OEM technical bulletins.
The M115.954's primary reliability risk is camshaft lobe wear on early builds, with elevated incidence in high-load and extended oil interval conditions. Internal Mercedes-Benz quality reports from 1979 indicated a notable share of pre-1978 engines requiring camshaft replacement before 120,000 km, while UK DVSA records link valve train noise to inadequate lubrication in older inline-six engines. High-load cycles and infrequent oil changes increase cam and lifter stress, making oil quality and interval adherence critical.
Analysis derived from Mercedes-Benz technical bulletins (1976-1980) and UK DVSA failure statistics (2015-2023). Repair procedures should follow manufacturer guidelines.
The most common questions about engine codes, what they mean, how to find them and how this database works
The M115.954 delivers smooth inline-six performance and is generally robust when properly maintained. Early models (1976–1977) are prone to camshaft lobe wear, but post-1978 revisions significantly improved durability. Regular oil changes with SAE 20W-50 API SF oil and timely replacement of known wear items (carburetor, gaskets) ensure long-term reliability.
Key issues include camshaft lobe wear (especially pre-1978), carburetor hesitation or flooding, thermal reactor blockage, and valve cover oil leaks. These are well-documented in Mercedes-Benz technical bulletins. Exhaust manifold cracking and distributor wear are also reported but less critical.
The M115.954 was used in the W114/W115 280 series (1976–1980), W116 S-Class (280S, 280SE, 1976–1979), and R107 SL-Class (280SL, 1977–1980). It replaced the M115.953 and was succeeded by the M115.955. All applications are longitudinal front-engine layouts with 4-speed manual or automatic transmissions.
Limited tuning potential exists. Carburetor upgrades (e.g., dual carbs) or conversion to fuel injection can yield +20–30 kW gains. However, the SOHC design and 9.0:1 compression limit major power increases without internal modifications. Performance camshafts and exhaust headers offer moderate improvements. Always maintain factory cooling and oiling systems when modifying.
Expect 15–18 L/100 km (16–19 mpg UK) in city driving and 10–12 L/100 km (24–28 mpg UK) on highways. Combined consumption typically ranges 12–14 L/100 km (20–24 mpg UK). Real-world figures depend heavily on driving style, given the carbureted engine's sensitivity to throttle use. Using premium fuel (98 RON) can improve smoothness and responsiveness.
Yes. The M115.954 is an interference engine. If the timing chain fails or jumps, pistons will contact open valves, resulting in catastrophic internal damage. This underscores the importance of timely maintenance and immediate attention to any timing-related noises or faults.
Mercedes-Benz specifies SAE 20W-50 oil meeting API SF standard. Use only high-quality mineral or semi-synthetic oil designed for high-load petrol engines and change it every 12,000 km or annually. Proper oil selection is critical for camshaft lubrication and long-term reliability.
Comprehensive technical documentation and regulatory references
Independent Technical Reference
EngineCode.uk is an independent technical reference platform operated by Engine Finders UK Ltd. We are not affiliated with MERCEDES-BENZ or any other manufacturer. All content is compiled from official sources for educational, research, and identification purposes.
Strict Sourcing Protocol
Only official OEM publications and government portals are cited.
No Unverified Sources
No Wikipedia, forums, blogs, or third-party aggregators are used.
Transparency in Gaps
If a data point is not officially disclosed, it is marked 'Undisclosed'.
Regulatory Stability
EU regulations are referenced using CELEX identifiers for long-term stability.
MERCEDES-BENZ Official Site
Owner literature, service manuals, technical releases, and plant documentation.
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.
Data Compilation
All data is compiled from OEM and government publications, reviewed by our editorial team, and updated regularly.
Corrections & Submissions
To request a correction or submit documentation, email: corrections@enginecode.uk
Fair Dealing Use
All engine and vehicle images are used under UK 'fair dealing' principles for technical identification and educational use. Rights remain with their respective owners.
Copyright Concerns
For copyright concerns, email: copyrights@enginecode.uk
GDPR Compliance
EngineCode.uk complies with UK GDPR. We do not collect personal data unless explicitly provided.
Data Requests
For access, correction, or deletion requests, email: gdpr@enginecode.uk
Trademark Notice
All trademarks, logos, and engine codes are the property of their respective owners. Use on this site is strictly for reference and identification.
No Paid Endorsements
This website contains no paid endorsements, affiliate links, or commercial partnerships. We do not sell parts or services.
Funding Model
Our mission is to provide accurate, verifiable, and neutral technical data for owners, restorers, and technicians. This site is self-funded.
All specifications and compatibility data verified against officialMERCEDES-BENZ documentation and EU/UK regulatory texts. Where official data is unavailable, entries are marked “Undisclosed”.
All external links open in new tabs. Please verify current availability of resources.