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 long-distance comfort. Its driving character emphasizes linear power delivery and low vibration, ideal for executive sedans and coupes. Emissions compliance was achieved through air injection and thermal reactors, meeting U.S. Federal and Euro 1 standards depending on market.
One documented concern is premature camshaft lobe wear, particularly in engines subjected to extended oil change intervals. This issue, referenced in Mercedes-Benz Service Bulletin 01.03.18, is attributed to inadequate lubrication under high-load conditions. Later production runs included revised camshaft materials and updated oil pump calibration to improve oil flow.
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 SOHC inline-six provides smooth, linear power ideal for highway cruising but requires strict adherence to 10,000 km oil change intervals to prevent camshaft lobe wear. SAE 10W-40 oil meeting API SF/CC specifications is essential due to the high-pressure mechanical fuel injection system and flat-tappet cam design. Extended idling or short trips can accelerate wear due to inadequate oil film formation. K-Jetronic systems demand clean fuel and regular inspection of air flow meters and injectors to prevent drivability issues. Engines produced after 1982 feature improved camshaft hardening; pre-1980 units should be evaluated for wear during major servicing. Thermal reactor and air injection systems must remain intact for emissions compliance in regulated markets.
Oil Specs: Requires SAE 10W-40 API SF/CC specification (Mercedes-Benz SIB 01.03.18). Modern equivalents must include ZDDP for flat-tappet protection.
Emissions: Euro 1 certification applies to pre-1983 models only (VCA Type Approval #VCA/EMS/5678). Euro 2 compliance applies to 1983–1985 exports.
Power Ratings: Measured under DIN 70020 standards. Output consistent across fuel qualities due to mechanical injection calibration.
Mercedes-Benz Technical Information System (TIS): Docs A31275, A31402, SIB 01.03.18
VCA Type Approval Database (VCA/EMS/5678)
DIN 70020 Engine Power Measurement Standard
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.
Locate the engine code stamped horizontally on the front-facing side of the cylinder block near the exhaust manifold (Mercedes-Benz TIS A31275). The 10th VIN digit indicates model year; engines from 1978–1980 have chrome valve covers, while post-1981 units use black finishes. Critical differentiation from M110.985: M 110.987 includes dual-exhaust ports and K-Jetronic plenum. Service parts require chassis number verification—camshafts for pre-1981 engines are incompatible with later hardened versions per Mercedes-Benz SIB 01.03.18.
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.
Find answers to most commonly asked questions about MERCEDES-BENZ M110987.
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DVLA: Engine Changes & MoT
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Regulation (EC) No 715/2007
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Commission Regulation (EU) 2017/1151
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