How Flow Rate and Viscosity Affect Filter Performance

What are the effects of flow rate, contaminant level and viscosity on the performance of a filter?

Oil Filter

Article originally published on

Relative to flow-rate, the efficiency, or Beta ratio, of a filter may change slightly but this is generally not that significant unless you are talking about wide extremes of flow. We can test an element rated at 30 GPM at flows ranging from 10 to 50 GPM without much change in Beta. We will, however, see a change in the initial (clean element) differential pressure and the dirt capacity of the filter. Pressure drop increases roughly proportional to the flow and the dirt capacity will decrease with increasing flow, but not necessarily linearly.

If dirt ingression is within reasonable limits there will be little effect on the Beta ratio or dirt capacity.

(read the entire article, "The Effect of Flow Rate and Viscosity on Oil Filter Performance,"...)