The Mercedes-Benz M166 and M266 were four-cylinder petrol engines. Manufactured in Stuttgart-Untertürkhiem, the M166 engines were produced from 1997 to 2005, while the M266 engines were produced from 2004 to 2013.
The M166 and M266 engines had aluminium blocks and cylinder heads, five main bearing crankshafts, electronic fuel injection, a single overhead camshaft (chain-driven) and two valves per cylinder.
The M166 and M266 engines were specially designed for vehicles with Mercedes-Benz’s ‘sandwich’ design whereby the engine and transmission were positioned to slide underneath the vehicle’s floor – rather than enter the passenger compartment – in the event of a severe frontal impact. As such, the engines were transversely mounted, positioned behind the front axle and tilted 60 degrees forward. Within the engine bay, only the cylinder head and maintenance points are easily accessible.
The M166 engines were available with five-speed manual, five-speed automatic and five-speed semi-automatic engines (the latter with an electronically-controlled clutch). While the M266 engines continued to be offered with five-speed manual transmissions, the other options consisted of six-speed manual and continuously variable transmissions.
| Engine | Code | Capacity | Peak power | Peak torque |
|---|---|---|---|---|
| M166 E 14 | 166.940 | 1397 cc | 60 kW at 5000 rpm | 130 Nm at 3750 rpm |
| M166 E 16 red. | 166.960 red. | 1598 cc | 60 kW at 5000 rpm | 140 Nm at 2400 rpm |
| M166 E 16 | 166.960 | 1598 cc | 75 kW at 5250 rpm | 150 Nm at 4000 rpm |
| M166 E 19 | 166.990 | 1898 cc | 92 kW at 5500 rpm | 180 Nm at 4000 rpm |
| M166 E 21 | 166.995 | 2084 cc | 103 kW at 5500 rpm | 205 Nm at 400 rpm |
| M266 E 15 | 266.920 | 1498 cc | 70 kW at 5200 rpm | 140 Nm at 3500-4000 rpm |
| M266 E 17 | 266.940 | 1699 cc | 85 kW at 5500 rpm | 155 Nm at 3500-4000 rpm |
| M266 E 20 | 266.960 | 2034 cc | 100 kW at 5500 rpm | 185 Nm at 3500-4000 rpm |
| M266 E 20 AL | 266.980 | 2034 cc | 142 kW at 5000 rpm | 280 Nm at 1800-4850 rpm |
