Electrostatic filtration does not affect soluble additives. It can remove insoluble additives.
We recently tested our newest BCA machine in an injection molding hydraulics application. Even though the ISO numbers were great and the oil was just a few years old, the oil was full of submicron contaminants. we started with a gravimetric of 240mg/100ml. After about 2 weeks of electrostatic filtering the grav. read 6mg/100ml. Electrostatic filtering was clearly superior to the bypass micro-filter they had in the system.
The problem really comes down to costs of the oil and the problems you are seeing in maintenance of the hydraulic system. If you have a small quantity of oil and very little in hydraulic problems, a filter is the right choice. If you have a lot of sumps, and serious hydraulic component problems, electrostatics are worth the expense. For more information about the test results, email me or call.