[Werner]

Sponsored Links (Register now to hide all advertisements)

The contamination of the oil by foreign dust etc. is trapped by the filter.

But this has little influence on the color of the oil. Oil gets darker due to the soot from the combustion entering the oil circuit. If this soot is held in suspension by the oil additives so that it can not settle into the interior of the engine, the oil quickly turns black because the dissolved thin soot can not be retained much by the filter.

I would like to say that the color of the oil is hardly dependent on whether a filter is installed or not. The darkening depends on the formation of very fine soot, which occurs especially with a rich mixture on idle and cold running. If you use a good mineral oil over API "SC", the soot remains in suspension and will be flushed out the next time you change oil. In non-cleaning oils (API "AA" or "AB"), the soot inside settles and gradually decomposes into tar in the sump.