When considering the best automotive or industrial filter for your equipment, it may seem a like brand name will automatically tell you the quality of the product, but quality goes far beyond the name on the packaging. One way to gauge the quality is by understanding the use of micron ratings.

What is micron rating?

A micron is the unit of measure used for filter products: it is equal to 10-6 or one millionth of a meter or roughly 39 millionths of an inch. The micron rating is vital to the production of high-quality filters because it gives the end-user an indicator of how well the filter will remove contaminants from liquid such as oil and fuel. For example, if a filter shows a micron rating of 9, it will filter out particles 9 microns and larger.

Absolute micron rating

An absolute micron rating indicates the filter’s ability to remove at least 98.7% of contaminants with specific sizing. In order to determine this rating, the manufacturer must conduct single-pass or multi-pass testing to see how many specific sized particles are able to pass through.

Nominal micron rating

Nominal micron ratings indicate the filter’s ability to remove anywhere from 50% to 90-98.6% of contaminants at a particular size. This is also determined through the testing process, but can be considered somewhat unreliable due to conditions and inconsistent measuring. It is important to know the nominal micron rating, but when considering the two types, it is always better to consider the absolute micron rating.

When deciding what filter to use in your equipment, it is best to know both ratings as well as information such as beta ratios and the efficiency in order to make a truly informed decision. Knowing both the absolute and nominal micron ratings can give you a great overall view of your filters ability to protect your equipment for long-term use.