Here is some info off the web:
Fram Extra Guard PH8AThis filter cartridge has a small outside diameter with a rather low filter element surface area (193 sqin), and features cardboard end caps that are glued in place. The rubber anti-drainback valve seals the rough metal backplate to the cardboard end cap and easily leaks, causing dirty oil to drain back into the pan. If you have a noisy valve train at startup, this filter is likely the cause. The bypass valves are plastic and are sometimes not molded correctly, which allows them to leak. The backplate has smaller and fewer oil inlet holes, which may restrict flow.
Fram Tough Guard TG8AThis filter has an improved filter element with more surface area (248 sqin), a heavy silicone anti-drainback valve with a good sealing surface, the same plastic pressure relief valve but with an integral screen to keep out large particles, and enough inlet holes for good flow. In my opinion, the only real drawback to this filter is that it is capped on each end with cardboard instead of metal.
Fram Double Guard DG8AThis is one of the most expensive filters you can buy. Inside is a basic Fram Extra Guard (PH8A) filter element that has larger diameter holes at the end and has been pre-oiled. You can see this in the picture above I assume this is to hold the Teflon particles in the filter element before the unit is installed. Don't put Teflon in your engine. It does not belong there! DuPont does not recommend using their Teflon product in internal combustion engines.
Mobil 1M1-301
Like the Champ filter, this filter is made by Champion Labs. However, it uses a unique end plate and a thicker can that make it the strongest filter available for wide distribution retail sale. It also uses a synthetic media, which inproves filtration and flow. I'm happy to say that this filter is not a fake. It is definitely a unique design.
It uses a synthetic fiber element that can filter out very small particles and is very strong. It is rated just under the Purolator Pure One as far as filtering capability, but is still very much above conventional paper filters. It also has a very strong construction to withstand high pressure spikes during start-up. However, as with all Mobil 1 products, expect to pay 2 - 3 times as much for this filter.
WixThese filters are manufactured by the Dana corporation, who also manufactures all of the Wix clones. These include NAPA and many OEM filters.
This filter has metal cartridge end caps, but has a separate bypass valve that rests against the bottom end cap, like the AC Delco. I refer to this as a two-piece filter cartridge. Like the Champion, it uses an anti-drainback valve that doubles as the bypass valve-to-backplate seal. Instead of the leaf spring spacer that most filters use, these use a stiff coil spring at the top of the cartridge. Like the Purolator, the filter element paper media is stronger than the Champion media. The only drawback to this design is that the bypass valve seats metal-to-metal against the bottom cartridge end plate. This could allow dirty oil to seep from the dirty side to the clean side of the filter, bypassing the element. The design will not allow oil to seep back into the pan, though and the amount of oil that can get past is probably negligable.
PurolatorPremium Plus L30001Here is a fairly well designed filter, especially for the price. One odd thing about Purolator's filters is a string that is always wrapped around the filter element. I assume that this is there to hold the element in place while the glue in the end caps cures. Of all the Purolator-based filter I tested, there was one (the ProLine) that had filter element damage from this string. Although it was one of five tested, I am weary of this design. Even though the element was crushed a bit, it was not ripped.
The filter cartridge has an impressive surface area of 316 sqin, which is very close to the AC Delco Duraguard. The difference is that Purolator's filter element is compressed into more pleats (51) than the AC Delco. This may restrict flow somewhat, but not as much in this model than the Pure One. It features a spring-loaded metal bypass valve and a nitrile rubber diaphram-type anti-drainback valve, which doubles as the seal between the backplate and the cartridge. Like the Champion, this bypass valve is stamped right into the bottom end cap of the cartridge, so it is all one piece.
