We are happy to reply to every question from you,
but in order to save time we recommend that you glance at the questions that we
frequently encounter. Perhaps you’ll find the answer that you’re looking for.
Because the use of old and dirty oil that has lost its characteristics − just like a lack of oil − is liable to cause serious damage, from the build-up of soot and deposits that cause accelerated wear, down to ruin of the engine.
In a garage, during every regular service as instructed by the manufacturer: changing the engine oil and the filter is part of the service.
This is certainly recommended, since dirt is frequently trapped in the filter, and if the filter is not changed it will seep into the new oil, which would be a pity.