They come in a wide variety of configurations ranging from small sections attached to full-flow filters to spinning filters, to remotely mounted filters. All claim to filter to a much smaller micron size. Most do, but what is most important is how efficient they are at filtration. A micron rating can be misleading if the filter is inefficient at that micron level. All second generation filters have no, or very limited, ability to remove liquid contaminants such as fuel, water, or coolant from the oil.
Liquid contaminants lead to oil break down, acid pitting, and viscosity loss.
Improved Third Generation Oil Filters Third generation filters add the ability to remove liquid contaminants to the finer particle filtration achieved by second generation filters. This significantly changes the abiltiy of the filtration system to extend oil life. By removing both liquid and solid contaminants, the additive package in the oil has less to do and so it lasts longer. Fine particle filtration reduces wear as shown by SAE reports and independent oil analysis. Keeping the oil clean means oil drain intervals can be safely extended without compromising durability and it can easily be monitored with oil analysis.