Oil filter

The pressure drop is measured at the before and after the oil goes through the filter. So you will need two pressure gauges. The stock oil pressure gauge up top the engine is after the filter. Now you need to find or make a spot to check the pressure going into the filter.

I don’t think it a big deal for a stock or mildly hopped up engine, but if it means a lot to you, then check, try out filters (since no filter of worth was named by those who quibble about it as an issue) and please do so report back.

You could probably cut down on the amount of filters purchased for the trials but looking at the manufacturers web sites. You may be surprised at what you find in print and reality.