Choosing the right oil for a DPF diesel

The grade printed on the oil cap — 5W-30, say — describes viscosity and nothing else. Two oils can share it and still be completely unsuitable for each other's engines. On anything with a diesel particulate filter, the specification that matters is the ash content.

SAPS, and why it blocks filters

SAPS stands for sulphated ash, phosphorus and sulphur. Those additives protect the engine, but they do not burn away — they collect in the particulate filter as ash. A full-SAPS oil in a DPF engine will shorten the filter's life dramatically, and a blocked filter is not a warranty claim.

Read the ACEA rating, not the viscosity

• ACEA C1 / C2 / C3 / C4 — low or mid SAPS, formulated for filters and catalysts.
• ACEA A3/B4 — full SAPS. Excellent oil, wrong application for a DPF.

Manufacturer approvals sit on top of that and are stricter still. Where a vehicle names one, fit an oil carrying it — the approval is the manufacturer confirming that specific formulation, not just the category.

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Written for Redline Motor Factors — a demonstration store. See the AgenticEcom Suite.