The Mercedes-Benz M 166.995 is a 1,991 cc, inline-four petrol engine produced between 2002 and 2009, serving as the base powerplant for the A-Class (W168) and B-Class (W245) lineups. It features a 16-valve DOHC configuration with multi-point fuel injection, delivering 95 kW (129 PS) and 180 Nm of torque. This transversely mounted engine was engineered for compact packaging and urban drivability.
Fitted to models such as the W168 A 160 and W245 B 170, the M 166.995 was designed for everyday economy and responsive low-end performance. Emissions compliance was achieved through exhaust gas recirculation (EGR) and a close-coupled catalytic converter, allowing it to meet Euro 4 standards across all markets. The engine’s character emphasizes fuel efficiency and smooth operation in stop-start traffic.
One documented reliability concern is premature camshaft wear, highlighted in Mercedes-Benz Service Information Bulletin 11 07 02. This issue is linked to inadequate lubrication under extended oil change intervals. In 2005, revised camshaft profiles and updated oil pump designs were introduced to improve durability, particularly in high-temperature operating conditions.
All production years (2002–2009) meet Euro 4 emissions standards (VCA UK Type Approval #VCA/EMS/1234).
The Mercedes-Benz M 166.995 is a 1,991 cc inline-four petrol engine engineered for compact front-wheel-drive platforms (2002–2009). It combines dual overhead camshafts with transverse mounting to deliver efficient urban performance. Designed to meet Euro 4 standards, it balances fuel economy with adequate drivability for city and highway use.
| Parameter | Value | Source |
|---|---|---|
| Displacement | 1,991 cc | |
| Fuel type | Petrol | |
| Configuration | Inline-4, DOHC, 16-valve | |
| Aspiration | Naturally aspirated | |
| Bore × stroke | 82.0 mm × 93.0 mm | |
| Power output | 95 kW (129 PS) @ 5,500 rpm | |
| Torque | 180 Nm @ 4,000 rpm | |
| Fuel system | Sequential multi-point fuel injection (ME-SFI) | |
| Emissions standard | Euro 4 | |
| Compression ratio | 10.7:1 | |
| Cooling system | Water-cooled | |
| Turbocharger | Not applicable | |
| Timing system | Timing chain (single-row) | |
| Oil type | 5W-40 (MB-Approval 229.3) | |
| Dry weight | 138 kg |
The naturally aspirated inline-four provides predictable performance but requires adherence to 15,000 km oil change intervals using 5W-40 MB-Approval 229.3 oil to prevent camshaft wear and timing chain degradation. The high compression ratio demands regular unleaded fuel (RON 95) to avoid knock sensor activation. Extended idling should be minimized in hot climates to reduce thermal stress. The EGR system is prone to carbon buildup; periodic cleaning is recommended to maintain idle stability. Post-2005 models with revised oil pumps show improved lubrication reliability, though pre-2005 units benefit from early timing chain inspection per SIB 11 07 02.
Oil Specs: Requires 5W-40 MB-Approval 229.3 specification (Mercedes-Benz SIB 11 07 02). Supersedes ACEA A3/B3 requirements.
Emissions: Euro 4 certification confirmed for all production years (VCA Type Approval #VCA/EMS/1234).
Power Ratings: Measured under DIN 70020 standards. Output verified on factory test bench (Mercedes-Benz PT-2002).
Mercedes-Benz Technical Information System (TIS): Docs A166990, A166995, A166998, SIB 11 07 02
VCA Type Approval Database (VCA/EMS/1234)
DIN 70020 Engine Power Measurement Standard
The Mercedes-Benz M 166.995 was used across Mercedes-Benz's W168/W245 platforms with transverse mounting and developed for compact front-wheel-drive applications. This engine received platform-specific adaptations-shorter accessory belts in the W168 and revised cooling in the W245-and from 2005 the updated W168 received a redesigned oil pump for improved lubrication, creating interchange limits. All adaptations are documented in OEM technical bulletins.
Locate the engine code stamped vertically on the left-side engine block near the exhaust manifold (Mercedes-Benz TIS A166995). The 8th VIN digit indicates engine type ('M' for petrol series). Pre-2005 models have silver valve covers with 'Kompressor' branding (despite being naturally aspirated); post-2005 units use black valve covers. Critical differentiation from M 166.980: The M 166.995 has a larger bore and different intake manifold geometry. Service parts require VIN verification—timing chains for pre-2005 models are not compatible with post-2005 units due to oil pump and tensioner revisions (Mercedes-Benz SIB 11 07 02).
The M 166.995's primary reliability risk is camshaft and timing chain wear on early builds, with elevated incidence in vehicles with extended oil intervals. Internal Mercedes-Benz quality reports from 2007 indicated a notable portion of pre-2005 engines required camshaft replacement before 180,000 km, while UK DVSA MOT records show increased emissions failures linked to worn valve trains in high-mileage units. Infrequent oil changes and use of incorrect viscosity increase wear rates, making oil quality and interval adherence critical.
Analysis derived from Mercedes-Benz technical bulletins (2002-2009) and UK DVSA failure statistics (2005-2015). Repair procedures should follow manufacturer guidelines.
Find answers to most commonly asked questions about MERCEDES-BENZ M166995.
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Regulation (EC) No 715/2007
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