Based on testing by others I still think this is a really good filter. The AMSOIL SDF-20 filter is well constructed and lab tests show that it's an excellent filter. On the other hand, it's big brother the SDF-44 did not filter oil well at 13,000 miles. Proving that an oversized filter is not always a good thing when it comes to filtration. The K&N HP-1004 is a great filter.
This filter is meant to maintain higher flow while still actively filtering, as opposed to by-passing. Lab tests using Mobil 1 at 7500 miles indicates that this filter works as well as the AMSOIL SDF-20. The FRAM x2 (and only the FRAM x2 Series) is probably the most heavily constructed filter I've seen so far. Though all of the Japanese made filters were of exceptional quality, the Fram x2 was as good in every way. Of note with the construction were the following features: metal screen backing the media, heavy metal end caps (purolator oil filter 1998 jeep cherokee have cardboard), and 2 layer filter medium. Lab testing indicates this filter is fine at 5000 miles use with Mobil 1.
However, lab tests do not indicate that the valve jams or fails to work. It's possible that a hard enough impact at a sharp angle while the purchase order was by-passing might cause it to jam open, but I suspect the fluid within the filter would prevent this. While both the STP and the Bosch filters were at one point good filters, they are now manufactured off shore of sub-standard parts. The filter assemblies tended not to have even pleats and generally less media than other comparable filters. There was also a complete lack of a well functioning by-pass valve. With most filters there is an obvious and discrete by-pass valve, but with these filters the can spring and the by-pass valve are the same. The real issue is that in order for the filter to properly by-pass the entire poster assembly would have to move down during use. That is actually not possible with filter assembly properly seating into the anti-drain back valve. This means that the by-pass will effectively never work. In the center of the of picture below you see the filter assembly (top) and the can spring/by-pass valve (bottom). A serious word of caution to experimenters: if you are thinking of trying out different/oversized filters, or ones we haven't listed here, be careful. In the course of testing, we tried a Purolator PureOne oversized oil filter cutter; it leaked pretty bad. Upon inspection, the gasket was found to be MUCH too large, large enough that the oversized M1-105 filter (and M1-104, OEM size) gasket actually fit inside it. If you experiment, be very careful, and look over the filter before testing it. Check the filter immediately upon starting the motor and look for leaks.
Also keep in mind the difference in bypass spring pressures as this may dramatically affect the way your vehicle's oiling system operates. Check with the storyteller manufacturer for exact bypass spring specs, most will usually provide this information via simple email contact with you.
But when I finally got smart and pulled out the dremel tool with the cutting wheel, that did the trick.
This analysis covers some basic key-measures of these oil filters.
Also, I am not an oil filter expert, I've just been maintaining my own cars probably like most of you and have been doing it since I started driving at 14, today I'm 50.
I'm maintaining 5 cars right now (2 for me, wife's, daughter's, and son's). I've owned a lot of cars, probably 20 or so including pick-ups.
I think Corolla is the highest value vehicle made today, just my opinion, its a great around town car that has the capability of making fairly pleasant interstate trips and it doesn't beat you up to bad in the process. I've bought fram oil filters for atvs for this report that I thought were good quality and that an average guy might use. Over the years, I've bought about every oil filter brand out there. I've never really known what was inside oil filters either, or much about how they worked. I imagine there are engineers out there that spend an entire career designing oil filters. I know a whole lot more today than I did, so its been worth the effort. I can see there is a lot of science, both design, material and production, in oil filters. Certainly more than I ever thought there was.
