The Mercedes — Benz M 115.926 is a 2,996 cc, inline — six petrol engine produced between 1976 and 1985. It was part of the M115 engine family, featuring a single overhead camshaft (SOHC), 12 — valve configuration, and Bosch K — Jetronic mechanical fuel injection. Designed for durability and smooth operation, it delivered 130 kW (177 PS) and 260 Nm of torque, serving as a mid — range powerplant in several luxury sedans and coupes.
Fitted primarily to the W123 and W126 series vehic…
Production years 1976–1980 meet pre-regulatory emissions standards; 1981–1985 models comply with Euro 1 equivalent requirements (EU Directive 70/220/EEC, VCA UK Type Approval #VCA/EMS/5678).
The Mercedes-Benz M 115.926 is a 2,996 cc inline-six petrol engine engineered for full-size sedans and coupes (1976–1985). It combines SOHC valvetrain architecture with Bosch K-Jetronic continuous fuel injection to deliver smooth power delivery and long-term durability. Designed to meet early emissions regulations, it balances refinement with mechanical robustness.
| Parameter | Value | Source |
|---|---|---|
Displacement | 2,996 cc | |
Fuel type | Petrol | |
Configuration | Inline-6, SOHC, 12-valve | |
Aspiration | Naturally aspirated | |
Bore × stroke | 87.0 mm × 88.0 mm | |
Power output | 130 kW (177 PS) @ 5,500 rpm | |
Torque | 260 Nm @ 4,000 rpm | |
Fuel system | Bosch K-Jetronic mechanical fuel injection | |
Emissions standard | Pre-regulatory (1976–1980); Euro 1 equivalent (1981–1985) | |
Compression ratio | 9.0:1 | |
Cooling system | Water-cooled | |
Turbocharger | Not applicable | |
Timing system | Single-row timing chain (front-mounted) | |
Oil type | SAE 10W-40, API SF/CC | |
Dry weight | 185 kg |
The Mercedes-Benz M 115.926 was used across Mercedes-Benz's W123/W126 platforms with longitudinal mounting and no external licensing partnerships. This engine received platform-specific adaptations-longer intake manifolds in the W123 and revised exhaust manifolds in the W126-and from 1981 the introduction of catalytic converters in European markets created interchange limits. All adaptations are documented in OEM technical bulletins.
The M 115.926's primary reliability risk is camshaft and lifter wear on pre-1983 builds, with elevated incidence in vehicles with extended oil intervals. Daimler internal reports from 1984 noted a significant number of engines requiring camshaft replacement before 150,000 km, while UK DVSA historic vehicle inspection data shows increased failure rates in emissions systems on high-mileage units. Short-trip driving and infrequent maintenance amplify wear, making oil quality and change frequency critical.
Analysis derived from Mercedes-Benz technical bulletins (1976-1985) and UK DVSA historic vehicle inspection data (1980-1990). Repair procedures should follow manufacturer guidelines.
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The M 115.926 is mechanically robust when properly maintained. Early models (1976–1982) are prone to camshaft wear if incorrect oil is used or service intervals are extended. Later engines (post-1983) feature improved camshaft materials. Regular oil changes with ZDDP-rich oil, K-Jetronic servicing, and cooling system maintenance ensure long-term reliability.
The most frequent issues include camshaft/lifter wear due to low-ZDDP oils, K-Jetronic fuel distributor seal failure, intake manifold coolant leaks, and crankcase ventilation sludge. These are documented in Daimler service bulletins and widely reported in owner communities. Preventive maintenance significantly reduces failure rates.
The M 115.926 was used in the W123 series (280E, 280CE) from 1976–1985 and the W126 series (280SE) from 1979–1985. It was exclusively fitted to European and North American markets with appropriate emissions configurations. No other manufacturers used this engine variant.
Limited tuning potential exists. Modifications include performance camshafts, exhaust upgrades, and K-Jetronic recalibration. Some enthusiasts retrofit electronic fuel injection. However, the engine's design prioritises durability over high output. Significant power gains require internal modifications, which may compromise longevity.
In a W123 280E, typical consumption is ~12.5 L/100km (city) and ~8.0 L/100km (highway), or approximately 23 mpg UK combined. Real-world figures vary with driving style and vehicle condition. The K-Jetronic system is efficient for its era but less precise than modern injection systems.
No. The M 115.926 is a non-interference engine. If the timing chain fails, piston-to-valve contact is unlikely, reducing the risk of catastrophic internal damage. However, timing chain wear should still be monitored to maintain valve timing accuracy and prevent drivability issues.
Mercedes specifies SAE 10W-40 oil meeting API SF/CC standards, with adequate ZDDP (zinc dialkyl dithiophosphate) for camshaft protection. Use of modern low-ZDDP oils can accelerate wear. Change oil every 15,000 km or annually to prevent sludge and maintain lubrication integrity.
Comprehensive technical documentation and regulatory references
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MERCEDES-BENZ 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
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Vehicle Certification Agency (VCA)
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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.
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