OM601

Introduced in 1983 in the W201 190 D and spreading to the W124 the following year, the OM601 replaced the OM616 and headed a family completed by the five-cylinder OM602 and six-cylinder OM603. All three shared an iron block with an aluminum head, a duplex chain driving camshaft and injection pump, and hydraulic bucket tappets that put an end to periodic valve adjustment. The genuine novelty was not inside the engine but wrapped around it: a bonnet mat, sealing strips, polymer skirts, an underpanel and a second bulkhead, with thermostatic vents to keep the sealed bay from cooking.

Mercedes-Benz claimed the encapsulation cut noise emissions to less than half those of comparable engines, and the 190 D was the first of its diesels to get it. Three displacements followed the market: two liters for Europe, 2.2 for North America where emissions rules demanded it, 2.3 for commercial work. Passenger cars moved to the four-valve OM604 in 1993, but the OM601 simply changed jobs, running on in the T1 208 D, 308 D and 408 D, the Vito, the first Sprinter and — turbocharged at last, as the 601.970 — the V 230 TD. It was still being built in 2000.