I just looked and the much criticized Fram says that their ratings are based on the ISO 4548-12 standard, so I suppose we can compare them directly to Purolator. Of course there is some vagueness still, but they claim 97% for the Extended Guard, 99% for the Tough Guard, and 95% for the Extra Guard, at >20 microns. It's even for the same size filter as the Purolator. Purolator claims 99.9% efficiency above 20 microns. The XG8A is equivalent to the PL30001 or the FL1A in Motorcraft.