4 to 5 litres is a fairly typical oil capacity or a family hatch with up to 20k between oil changes.

If a van has close to two times the capacity - does the oil degrade simply due to time elapsed, or at half the rate due to the greater capacity. If the latter, arguably twice the capacity = twice the length between oil changes.

"does the oil degrade simply due to time elapsed" (?)

No.

"or at half the rate due to the greater capacity"(?)

No

It'll be more complicated than either of those scenarios.

But for a given engine and use regime, if you could somehow double the sump capacity, it would probably extend the oil life, since you will dilute the contaminants, the average oil temperatures would tend to be a bit lower, and the oil would tend to shear down less due to spending less average time in high shear parts of the engine.

The obvious exception would be short tripping, which would tend to have a worse effect due to the lower average temperature of the oil causing condensation and fuel dilution buildup.

So it would depend...

OTOH IF it doubled the oil life, with the original sump capacity you could have done an oil change and used the same total amount of oil.

Edited by edlithgow on 07/12/2022 at 18:24