Motor oil filter contains an oil-soluble solid block - which replenishes the oil with additives

摘要

The ring-shaped block is placed at the stillest part of the oil filter, and outside the paper filter through which the oil must pass on its way from the entry to the exit. This allows the block to dissolve more steadily; and if a sizeable crumb should wash off, it will be retained by the paper filter and not pass directly into the oil circulation.