Mercedes-Benz CDI (badge, not an engine)

CDI is a badge, not an engine — Mercedes-Benz's word for a common-rail diesel, on Mercedes and Smart in this catalogue, from a 0.8 three-cylinder to a 4.0 V8.

⚑ The number on the boot is not the displacement. A 220 CDI is 2.1 or 2.2 litres; a 320 CDI is 3.0. Mercedes' badge numbers mark where a car sits in the range, not how big its engine is, so searching a part catalogue by the badge number finds nothing and the litre figure a listing prints may be either.

⚑ The same badge at the same size can be two different engines. The W203 C-Class was sold as a 2.1 CDI with the OM611 and later with the OM646 — different families, same badge, same displacement, same model. Only the year and the OM code separate them.

What the badge covers here:

• Four-cylinder — OM611, OM646, OM651, OM654, in that order over 25 years, plus OM640 in the A- and B-Class and OM668 before it.
• Five and six in line — OM612, OM613, OM648.
• V6 — OM642, the 3.0 in almost everything from the W211 onward.
• V8 — OM629, the 4.0.
• Three-cylinder — OM660 and OM639, the Smart diesels.

⚑ Not every CDI is a Mercedes engine. The Vito W447's 1.6 CDI is Renault-derived and drives the front wheels — the alliance running the other way from the K9K, which Mercedes sells as the OM607/OM608. A Mercedes badge is not a guarantee of Mercedes parts, and the service literature for that engine is Renault's.

Establish the OM code. It is on the engine and in the data card, and every family above has its own page here.