"Is there a risk of altering a lubricating or hydraulic oil with 1-micron or submicron filters? For instance, could they reduce the EP additives?"
There are several ways to strip additives from lubricants. Polar aggregate separators (for example, activated alumina), vacuum or thermal dehydration, centrifugation and absorbent depth filtration all present some risk. However, with careful planning, the risk can be minimized and the benefit of contamination control maximized.
There are some classes of additives that certainly can be removed with fine depth media filtration. Many types of lubricants have defoamant additives. These are semisolid suspensions in the 5- to 10-micron range and are filterable.
Efficient 1-micron filters can potentially remove EP (sulfur and phosphorus) additives that are not dissolved as well as suspended solid anti-scuff additives.