استهلاك مفرط للزيت

The engine burning oil, which reaches the diagnostic systems through what the oil does downstream. Oil in the combustion chamber fouls plugs, coats oxygen sensors and poisons the catalyst, so the codes name ignition and emissions rather than consumption.

Worn rings, worn valve stem seals and a failing turbocharger seal are the routes, and they are distinguishable by when the smoke appears — on start-up for stem seals, under load for rings, and on overrun or boost for a turbocharger. It also fills a particulate filter with ash, which is not combustible and ends that filter's life early. A filter reaching ash loading well before its expected mileage is worth taking to oil consumption, since replacing it without addressing that shortens the next one the same way.