Oil increase in diesel engines with DPF (Solution)

In diesel engines with a DPF (Diesel Particulate Filter), which are often operated in short-distance driving conditions, a mysterious increase in oil consumption frequently occurs.

Reason: "Active" DPF regeneration.

In "passive" regeneration (e.g., on the highway), the necessary exhaust gas temperatures (approximately 300-500°C) for particle combustion are reached during normal driving operation, without any intervention from the engine control unit.

In the case of "active" regeneration (e.g., frequent stop-and-go traffic/short trips), the engine control unit intervenes to generate the necessary temperatures within the diesel particulate filter (DPF) for particle combustion.

The additional fuel required is ensured, among other things, by extended injection times (well after top dead center).
Often, unburned fuel remains on the cylinder walls and then enters the engine oil from there.

Under unfavorable conditions, "active" regeneration can occur approximately every 200 to 400 kilometers, which can result in a significant amount of fuel entering the engine oil over an extended period.

The low oil temperatures (typical of city driving or short distances) also prevent the breakdown of the mineral components in the fuel.

Generally, it is said that oil dilutions up to 10% are not critical, but they are often present after only about 10,000 km of driving.

Recommendation: Regularly check the oil level and consider changing the oil more frequently for vehicles used primarily for short trips.

Faults that can also contribute to increased oil consumption, such as leaking PCVs (Positive Crankcase Ventilation valves), dripping injectors, etc., should be ruled out after a prior inspection.