I found this on a 300C forum posted by a member called Deep Lava. Some good info.
Oil Filters - Dissected
I was wondering what the differences were between some of the current oil filters. The study done at Engine Oil Filter Study is quite dated. So, I bought some oil filters from the local stores, grabbed my hacksaw and away I went. All filters had an anti-back flow gasket.
The basic Fram is still crap. Fewest pleats and therefore least amount of filter area. Cardboard end-caps.
The TG Fram is better. Still has cardboard end-caps but has 15% more filter media and a screened by-pass valve.
The XG Fram is, can't believe I'm saying this, a decent filter. This is the only filter tested that used a different type of filter media. It was more fiberglass in nature vs. paperish for all the rest and is supported with a metal mesh. So even though it has less area, it is 2-3 times as thick.
STP and SuperTech are the exact same filter. Decent filter area but cheaply made and the felt end caps detached from the filter media with frightening ease. No by-pass valve.
Mopar and Purolator PremiumPlus are the exact same filter. Plenty of filter media with metal end caps which are impossible to remove from the filter media as seen by the dead Mopar filter.
Purolator PureOne and Bosch are the exact same filter. Largest amount of filter media with metal end caps which are also impossible to remove from the filter media.
All four of the latter are made by the same manufacture with the only difference between the two sets is the Mopar/Purolator PremiumPlus has the by-pass valve in the front, built into the stem..
...and the Bosch/Purolator PureOne has the by-pass valve located in the back via a 45-speed record adapter spring thingy along with 4 more pleats of filter media. Also, the PureOne has the best paint job. A nice royal blue w/ pearl coat
The Wix and NAPA Gold are the same filter but the NAPA Gold had 4 more pleats (61 vs 57) than the Wix. Was this by design or was it a machine assembly variance, probably the latter since everything else was exactly the same. The filters were similar to the Mopar and the Purolator PremiumPlus but made by someone else. They had a similar stem based by-base which was not attached to the filter media but loosely sits in the end-cap without a gasket. The Wix and NAPA Gold also had the second least amount of filter media. They had metal end-caps with the filter media permanently attached.
The Mobil 1 and the K&N are exactly the same filter less the 1" bung thingy on the K&N. Both are heavy due to their thick bases and smaller inlet holes. They too had the stem based by-pass valve firmly attached to the end-cap but only had 55 pleats, the second fewest. It did have the deepest pleats which equals fifth in area and the filter media was slightly thicker than most. Had metal end-caps with the filter media permanently attached.
Question is... which one filters the best without restricting flow and has the most reliable bypass. Fram is known for bad bypass, K&N has been debated that it allows too much dirt. I'm surprised that Bosch is similar to the PureOne most everything Bosch makes for cars is junk. I've been using Purolator, Wix and Mopar.
Second highest filter area, construction level with all the 'best'... The only thing this test didn't do though was check how fine the filter media was, as in how far down will it filter contaminates... I'd bet they are all just about the same 'hole size' with the exception of XG Fram... and with out testing, I don't know if that is 'better' or not... But it probably cloggs a little more, or a little less, easily. Personally I'd bet it is less likely to clog... but I could be all wrong there...
Wow that was a lot of work and money.... Thanks strongT...
What do you guys think about amsoil filters?
How often do you change your oil, after how many miles? I do mine every 3000
I usually use fram tough gaurd and valvoline syn power oil.. Lately ive been using K&N filters and Valvolin syn power though. (I stocked up when advanced auto parts offered 5 qts of syn power and a K&N filter for $25)...
I have a used k&n filter and a used fram TG both with 3000 miles if anyone would like me to hack them open to see them after they've been used.