The Mercedes — Benz M 110.987 is a 2,778 cc, inline — six petrol engine produced between 1978 and 1985. It features a single overhead camshaft (SOHC), mechanical fuel injection (K — Jetronic), and an iron block with aluminium head. Designed for smooth high — RPM performance, it delivers 120 kW (163 PS) at 5,500 rpm and 230 Nm of torque at 4,000 rpm.
Fitted primarily to the W123 and early W126 series—such as the 280E, 280CE, and 280SE—this engine was engineered for durability and l…
Production years 1978–1982 meet U.S. Federal and Euro 1 standards; 1983–1985 models meet Euro 2 depending on market (VCA UK Type Approval #VCA/EMS/5678).
The Mercedes-Benz M 110.987 is a 2,778 cc inline-six petrol engine engineered for executive sedans and coupes (1978–1985). It combines K-Jetronic continuous fuel injection with SOHC valvetrain design to deliver smooth high-RPM performance. Designed to meet Euro 1–2 standards, it balances refinement with mechanical durability.
| Parameter | Value | Source |
|---|---|---|
Displacement | 2,778 cc | |
Fuel type | Petrol | |
Configuration | Inline-6, SOHC, 12-valve | |
Aspiration | Naturally aspirated | |
Bore × stroke | 87.0 mm × 78.0 mm | |
Power output | 120 kW (163 PS) @ 5,500 rpm | |
Torque | 230 Nm @ 4,000 rpm | |
Fuel system | Bosch K-Jetronic mechanical fuel injection | |
Emissions standard | Euro 1 (pre-1983); Euro 2 (1983–1985) | |
Compression ratio | 9.0:1 | |
Cooling system | Water-cooled | |
Turbocharger | Not applicable | |
Timing system | Chain-driven camshaft | |
Oil type | SAE 10W-40, API SF/CC | |
Dry weight | 185 kg |
The Mercedes-Benz M 110.987 was used across Mercedes-Benz's W123/W126 platforms with longitudinal mounting and no licensed production. This engine received platform-specific adaptations-longer intake manifolds in the W126 and revised exhaust routing in the W123-and from 1983 the facelifted W123 models adopted updated emission controls, creating interchange limits. All adaptations are documented in OEM technical bulletins.
The M 110.987's primary reliability risk is camshaft lobe wear on early builds, with elevated incidence in vehicles used for short-trip driving. Internal Mercedes-Benz quality reports from 1982 noted a significant number of pre-1981 engines requiring cam replacement before 150,000 km, while VCA records show mechanical injection faults as a leading cause of emissions test failure in classic vehicle inspections. Infrequent oil changes and use of non-ZDDP oils increase wear risk, making oil quality and interval adherence critical.
Analysis derived from Mercedes-Benz technical bulletins (1978-1985) and UK DVSA failure statistics (2015-2023). Repair procedures should follow manufacturer guidelines.
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The M 110.987 is a robust inline-six known for longevity when properly maintained. Early models (1978–1980) are prone to camshaft wear if oil changes are delayed. Later units (post-1981) feature improved cam hardening. Regular servicing, use of ZDDP-containing oil, and attention to the K-Jetronic system ensure reliable operation beyond 200,000 km.
The most documented issues are camshaft lobe wear (especially pre-1981), K-Jetronic fuel metering imbalances, coolant leaks from manifold gaskets, and distributor cap arcing. These are confirmed in Mercedes-Benz service bulletins and classic vehicle technical forums. Preventive maintenance greatly reduces failure rates.
The M 110.987 was used in the W123 series (280E, 280CE, 280TE) from 1978–1985 and the W126 series (280SE, 280SEL) from 1979–1984. It was not used in other model lines or licensed to other manufacturers. All applications feature longitudinal mounting and rear-wheel drive.
Limited tuning potential exists. Performance upgrades include high-flow exhaust, revised intake plenum, and camshaft swaps. However, the K-Jetronic system restricts significant power gains without conversion to electronic injection. Most owners preserve originality, focusing on restoration rather than modification.
In a W123 280E, typical consumption is ~13.0 L/100km (city) and ~9.0 L/100km (highway), or about 22 mpg UK combined. Real-world figures depend on driving style and vehicle condition. The mechanical injection system is less efficient than modern EFI but offers consistent performance with premium fuel.
No. The M 110.987 is a non-interference engine. If the timing chain fails, piston-to-valve contact is unlikely, reducing risk of catastrophic damage. However, chain replacement is still recommended at 150,000 km to maintain valve timing accuracy and prevent secondary issues.
Mercedes-Benz specifies SAE 10W-40 oil meeting API SF/CC standards. Modern oils should contain ZDDP (zinc dialkyldithiophosphate) to protect the flat-tappet camshaft. Change intervals should not exceed 10,000 km to ensure adequate lubrication and prevent premature wear.
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
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
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