Diesel engines with a particulate filter: oil and interval

Ash from the oil stays in the filter

A little engine oil always burns. The filter burns off the soot during regeneration, but not the ash from the additives: that stays in the filter for good. That is why manufacturers prescribe low-SAPS oil (ACEA C2, C3 or C4, plus their own approval such as MB 229.51 or VW 507 00). Regular oil leaves more ash and shortens the filter's life.

Fuel in the oil

During regeneration the engine injects extra diesel to heat the filter. If regeneration keeps being interrupted because the car is switched off after a short trip, part of that diesel ends up in the oil. The level rises and the oil thins — exactly when the engine needs protection.

If your diesel mostly does short trips, we advise a shorter oil interval than the service book, plus an occasional longer drive of twenty minutes or more at steady revs.

Signs to watch for

• The oil level rises between services.
• The fan keeps running after switching off, or idle speed is raised (regeneration in progress).
• A particulate filter warning on the dashboard.

Frequently asked questions

Can I use ordinary 5W-40 in my diesel?

Only if it carries your manufacturer's approval. For a diesel with a particulate filter that is almost always a C-class oil.

How often should a city diesel have an oil change?

With many short trips we advise once a year, even if the service indicator hasn't asked yet.

Can too much oil damage the particulate filter?

Yes. Excess oil can be burnt via the crankcase breather and add ash and soot to the filter.

See which oil suits your diesel in the service calculator or read more about the oil change in Tilburg.