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GSX/GSF Oil Filters Exposed!
A look at the Fram PH6018 and the STP SMO-18

Saving your motorycle from a potential disaster

The Fram PH6018, and STP SMO-18 are two common oil filters used in the GSX, and GSF family of air/oil cooled engines. These are commonly found in the Suzuki Bandit, Katana, and pre-1992 GSX-R motorcycles. While there are many other manufacturers of filters that work with these engines, the focus of this article is to provide a general idea of what makes a good or bad filter. The small picture quality isn’t great, so they’re linked them to larger, clearer versions. Just click on a picture to get an enlarged view.

The Fram PH6018

Fram PH6018 broken down

This is by far the poorest oil filter I have ever seen. The overall design isn’t bad (it isn’t great either, though), but the materials are sorely lacking in quality.The most alarming aspect of this filter, is the filter-element itself. The element has very few pleats in it compared to other filters. What does that translate into? Less filtering surface area. If you push more dirty oil through a smaller area, it will clog faster. Essentially, it has less ‘room’ to hold captured material.

The filter element utilizes cardboard endcaps. This is inherently stupid. When cardboard is exposed to very high temperature oil (200+ degrees), under pressure, it turns to mush pretty quickly. I was able to remove chunks of the material using little effort with my finger-nails. The internal O-ring seal cannot maintain a viable ‘sealed’ surface against ‘mushy cardboard’, suggesting that this filter may be prone to leaking unfiltered oil between the intake and exhaust channels within the filter.

Left: Filter element - Right: Bypass valve

The bypass valve assembly is fairly unremarkable, and I suspect the filter element would fail (i.e. rip, tear, burst, etc) before the bypass valve would actually have a chance to do its job. If this type of failure should occur, this filter is going to send a massive amount of crap into the engine, and thats assuming it doesnt clog all the outlets first, which means your engine could suffer from oil starvation. If I wanted to increase the odds of grenading an engine, this filter would most certainly be the ticket. This filter shows how NOT to make an oil filter. I recommend avoiding this filter at all costs.

The STP SMO-18

The STP is a fine example of what a good oil filter should be. The overall design is excellent, and the quality of materials and workmanship is top notch. The filter element has a substantial number of pleats, providing a large surface area for extended filtration. The higher number of pleats also increases the elements structural rigidity, and its overall tensil strength. Both are a definite bonus in a pressurized and high temperature environment.

The filter element utilizes metal endcaps. This element can withstand quite a bit of abuse in a pressurized environment, and is unlikely to ‘shread’ if there should be a problem. Another advantage to the metal endcaps is that it provides a substantial, and static, seal for the internal O-ring seal to work with. This makes it highly unlikely that this filter will allow leakage between the intake and exhaust channels.

The bypass valve assembly is intergrated in the lower endcap. The design of the bypass valve is pretty trick, it was obviously well thought out by the Engineer who designed it. It seems to incorporate an additional margin of safety just in its placement. It is protected by a large load-spring on the outside (which is not part of the valves operation), and a heavy-duty metal ’cap’ on the inside. This is a solid, well made, and highly functional oil filter. They way it should be done. I would recommend it to anyone who has an A/O cooled GSX/GSF based engine.

Griff, Maximum-Suzuki.com

Suzuki Bandit 1200, Suzuki Bandit 600, Suzuki Bandit 650, Suzuki Bandit 1250, Suzuki Katana 600, Suzuki Katana 750, Suzuki DR350, Suzuki DR-Z400, Forums.

Opinion Article #3 Februray 20th, 2002

The article reflects the opinions and observations of the author, and should not be used in scientific analysis. As always, it is up to the reader to form their own opinions and conclusions.