The Mercedes — Benz M110.923 is a 2,746 cc, inline — six naturally aspirated petrol engine produced between 1978 and 1985. It featured a cast — iron block, aluminium head, dual overhead camshafts (DOHC), and Bosch K — Jetronic continuous fuel injection. Delivering 135 kW (184 PS) and 250 Nm of torque, it was engineered for smooth, high — revving performance in executive coupes and sedans.
Fitted to key models including the W123 280E, W126 280SE, and C123 280CE, the M110.923 wa…
Production years 1978–1982 meet informal emissions standards; 1983–1985 models comply with Euro 1 .
The Mercedes-Benz M110.923 is a 2,746 cc inline-six naturally aspirated engine engineered for executive sedans and coupes (1978–1985). It combines DOHC 24-valve architecture with Bosch K-Jetronic continuous fuel injection to deliver smooth power delivery and long-term reliability. Designed to meet evolving emissions regulations, it balances refinement with mechanical durability.
| Parameter | Value | Source |
|---|---|---|
Displacement | 2,746 cc | |
Fuel type | Petrol | |
Configuration | Inline-6, DOHC, 24-valve | |
Aspiration | Naturally aspirated | |
Bore × stroke | 87.0 mm × 76.5 mm | |
Power output | 135 kW (184 PS) @ 6,000 rpm | |
Torque | 250 Nm @ 4,000 rpm | |
Fuel system | Bosch K-Jetronic (mechanical-electronic continuous injection) | |
Emissions standard | Pre-Euro (1978–1982); Euro 1 (1983–1985) | |
Compression ratio | 9.0:1 | |
Cooling system | Water-cooled | |
Turbocharger | Not applicable | |
Timing system | Single-row timing chain (non-interference design) | |
Oil type | Refer to vehicle handbook / manufacturer specification | |
Dry weight | 192 kg |
The Mercedes-Benz M110.923 was used across Mercedes-Benz's W123, W126, and C123 platforms with longitudinal mounting. This engine received platform-specific adaptations—longer intake manifolds in the W126 and revised exhaust manifolds in the C123—and from 1983 the updated oil pump and camshaft lubrication system improved durability, creating service part differentiation. All adaptations are documented in OEM technical bulletins.
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Field reports and technical service bulletins highlight component wear patterns under high-load operation. Adherence to manufacturer service intervals and approved fluid specifications is critical for long-term reliability.
Analysis derived from manufacturer technical service bulletins and industry workshop records. 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 M110.923 is fundamentally robust and capable of high mileage when properly maintained. Pre-1983 models are prone to camshaft wear if oil changes are delayed or incorrect oil is used. Post-1983 revisions significantly improved lubrication reliability. With regular servicing using MB 229.1 10W-40 oil and attention to fuel system components, these engines can exceed 300,000 km.
The most documented issues are camshaft/lifter wear (especially pre-1983), K-Jetronic fuel distributor faults, intake vacuum leaks, and thermostat housing leaks. These are confirmed in Mercedes service bulletins and technical workshops. Proper maintenance greatly reduces the likelihood of major failures.
The M110.923 was used in the W123 280E (1978–1985), W126 280SE (1979–1985), and C123 280CE (1980–1985). It was the DOHC inline-six variant for mid-range luxury models before being succeeded by the M103 engine family.
While not commonly tuned, modest gains are possible. Upgraded exhaust systems, performance air filters, and recalibrated fuel distributors can yield +10-15 kW. Camshaft swaps and induction modifications are feasible but require careful tuning. The engine's strong bottom end supports mild modifications, but the DOHC 24-valve head limits high-RPM potential.
In a W123 280E, real-world consumption averages 11.5–13.5 L/100km (21–25 mpg UK) in mixed driving. Highway efficiency improves to ~9.0 L/100km (~31 mpg UK). The K-Jetronic system is less efficient than modern injection but offers good drivability. Driving style and vehicle condition significantly affect observed economy.
No. The M110.923 uses a non-interference valvetrain design. If the timing chain fails, the pistons will not contact the valves, preventing catastrophic internal damage. This design enhances reliability and reduces repair costs in the event of timing component failure.
Mercedes specifies SAE 10W-40 oil meeting MB 229.1 standard. This viscosity ensures proper lubrication of the camshaft journals and lifters. Oil should be changed every 15,000 km or annually to prevent wear, especially in pre-1983 engines. Using correct oil is critical for long-term reliability.
Comprehensive technical documentation and regulatory references
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Regulatory Stability
EU regulations are referenced using CELEX identifiers for long-term stability.
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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