استخدام زيت محرك بمواصفة خاطئة

Oil that meets the viscosity but not the manufacturer's approval standard. On a vehicle with a particulate filter this matters more than viscosity does: low-ash oil exists because ordinary additives leave incombustible ash in the filter, permanently.

Ordinary oil shortens a filter's life dramatically. Ash accumulates far faster than designed, the filter reaches its restriction limit well before its expected mileage, and no amount of regeneration helps because ash does not burn. A filter ash-loaded early is worth taking to the oil rather than to the engine. The approval code is what matters, not the grade — two oils of identical viscosity can differ entirely in ash content, and the code is printed on the container beside the specification.