Engine oil Mercedes C-Class W205 OM651 (2.2 CDI) — viscosity and approvals

Which engine oil for Mercedes C-Class W205 OM651 (2.2 CDI, 2014–2021) — viscosity, specifications, capacity and change interval.

Engine Specifications

Recommended Oil

Change oil when either condition is reached — mileage OR time. Never exceed both limits simultaneously.

Approved Oil Brands

Castrol Edge 5W-30 LL / Mobil 1 ESP 5W-30 / Shell Helix Ultra ECT C3

How to Choose Oil for OM651

1. Viscosity must match specification — using the wrong viscosity grade is not acceptable. Only 5W-30 is approved for OM651.
2. Check the approval code on the label — the can must show ACEA C3 / MB 229.51 compliance. Regular oil with an incorrect approval may damage the engine.
3. Volume — when changing with a new filter, you need 6.5 L. Check the oil level with the dipstick 5 minutes after filling.
4. Do not mix grades — if topping up, use the same viscosity and specification.

Consequences of Using the Wrong Oil

• Oil with a wrong approval for a diesel engine can clog the DPF filter (diesel) or cause excessive oil consumption.
• Too thin oil (e.g. 10W-40 instead of 5W-30) accelerates timing chain/belt and crankshaft bearing wear.
• Too thick oil makes cold starting difficult and increases fuel consumption.

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What oil goes in a Mercedes C-Class W205 OM651?

Viscosity 5W-30, approval ACEA C3 / MB 229.51, volume 6.5 L. Recommended brands: Castrol Edge 5W-30 LL / Mobil 1 ESP 5W-30 / Shell Helix Ultra ECT C3.

How often to change the oil in Mercedes C-Class W205?

Every 10 000 km or 12 months — whichever comes first. With heavy city driving or short trips, every 7,500–10,000 km.

How much oil does the OM651 take?

6.5 litres with a new filter. Before ordering, double-check — some C-Class W205 variants with the same engine code may differ by 0.2–0.5 L.