Part of the fun in ATVs and Side x Sides is spinning wrenches from time to time and installing modifications. We’ve seen all manner of modifications over the years, from highly modified mud runners, to powerful motocross racers designed to soak up the biggest jumps with ease, to rock crawlers that can climb crab-like over boulders we can’t even walk up. The owners always love their ride, and they also love to talk about it, but we’ve never heard anybody brag about their oil filter. It’s ironic that one of the most important parts of the vehicle is so completely overlooked by so many. Ignore your oil too long, however, and we guarantee you will have plenty to talk about, first with the parts guy at your local dealer, and then with the lady at the bank as you undertake a major engine rebuild.
There are many oil filter brands on the market but only two main styles: either cartridge or screw-on. The cartridge filters are usually pretty straight forward and replaced by pulling a cover off the engine, pulling the old filter out, orienting the new filter in the correct direction, and putting the cover back on the engine. About the only thing that can go wrong is putting the filter in backwards which blocks off the oil passages, as some woeful Honda owners have found out the hard way - and by hard way, we mean expensive head work.
The screw on type oil filters are even easier to replace – provided you can get to it - but it got us wondering what exactly was inside the canister with all the holes on the bottom, and just what should we look for in a quality oil filter? Being inquisitive types by nature, we stopped at the local dealer, picked up a handful for our Suzuki KingQuad 750, and took them to the shop for some quality time with our disc grinder and cut-off wheel. Let the sparks fly and the investigation begin! 
Engine Primer
Most ATV and UTV engines operate on the same principal. Oil enters the oil pump through a screened intake located in the bottom of the engine and is forced by the pump into the oil filter housing. Once the oil is forced through the filter, cleaned, and returned to the motor, it is fed through passages to the head, bearings, crankshaft, connecting rods and wherever else the engine needs it. Oil thrown from the crankshaft or connecting rods also helps lubricate the pistons and cylinder walls. After doing its job on those parts, the oil trickles back to the bottom of the engine where the process repeats. Some ATV and UTV engines also route the oil through an oil cooler which is really a small radiator or heat exchanger that helps keep it cool. With the oil protecting so many important parts, keeping your oil clean is extremely important. It’s the first and last line of defense between you and engine destruction, and it’s the wrong time to bargain shop when buying filters or oil.
Most oil filters work as the oil flows (or more accurately is pressurized) on the outside of the filter and the pressure forces it through the filter surface or “media” where contaminants are trapped. The now clean oil then enters the engine to work its slippery magic. That’s simple enough, but it quickly brings us to one of the major factors in how well an oil filter performs - which is the dirt trapping media.
The filter media in most oil filters may look very much like folded paper, but it is actually an ultra-fine screen composed of very fine fiberglass strands, synthetic composite strands, or a combination of the two. By “ultra fine” we’re talking extremely tiny passages through the media as measured in microns. For reference, a human hair measures approximately 70 microns in diameter, and a single micron measures .000039 inches! Whatever the media is composed of, it’s the gaps or passages between each strand that determines what size particles will be trapped and which will pass through. The other major factor in filter media dirt stopping capability is the overall surface area, which is determined by the length, diameter, and the number and depth of the pleats. Unfold one of the pleated media pieces and it’s going to be a lot longer than you think! All the filter companies determine the size of the filter by measuring operating pressure, necessary flow volume, and then with the known pressure drop across their filter media, they can determine how much surface area they need to meet the required engine flow rates. Most oil filters also contain the following parts as well:
- Silicone Anti-Drain back Valve – A one-way valve that prevents oil from flowing back out of system when engine is shut off, insuring critical parts have instant lubrication on startup.
- Upper End Cap - retains element end sealant and holds filter media, provides an outlet for clean oil, and provides structural rigidity to the pleated media.
- Lower End Cap - retains element end sealant and holds filter media.
- Coiled Spring - ensures a constant load on the inner element to maintain the seal between the upper element end cap, the inner element support, and the mounting plate.
- Mounting Plate – has outer and inner passages, gasket ring, and mounts filter to engine
- Gasket - provides seal between the filter and engine
After opening up all the filters, it was time to see how they compared. Undoubtedly, the engineers at Suzuki gave the KingQuad a filter that met the engine’s needs so we used the Suzuki factory filter as the baseline for our comparison. 
Under the Covers
Stock Suzuki Oil Filter – There is really nothing fancy or special about the Suzuki oil filter, although since it is the factory filter for this engine, it must be adequate in flow rate and filtering capabilities as determined by the engineering staff. Inside the black canister (which is stamped with the all too common “made in China” statement) is a media cartridge of unknown micron passage diameter but it does have a silicone anti-drain back valve. It also has an overpressure / bypass valve at the top to allow flow in a cold start condition, or for when the owner ignores the filter too long and it becomes completely clogged. It’s a pity they don’t send somebody out to confiscate the quad from the undeserving owner at that point. The side of the filter is labeled with a part number and with the name WAKO, which we believe is the supplier.
EMGO Oil Filter – EMGO (named for company founder Emil Gomez) has a knack for finding an off-shore supplier in any number of low-cost Asian countries and bringing back a part that can serve as a direct OEM replacement. We’ve not always been impressed with the quality of some of these suppliers or parts, but we thought we should at least take a look since many dealers stock the EMGO brand as a low cost alternative. 
The EMGO replacement filter for our Suzuki looked to be identical to the factory filter in every way, although we did notice the exterior canister was a little thinner material. Once again, little is known about the filter media composition or micron passage size, but it did have an anti-drain back valve. The EMGO filter media actually had a slightly larger diameter than the stock Suzuki filter which gives it a little extra surface area for stopping contaminants. At the top of the end cap, the EMGO also had an overpressure / bypass valve for cold starts.
CARQUEST / WIX – Wix is a very large filter company and they have a complete line of their own, but they also “private label” filters for a few other companies. Buy a CarQuest filter and you are buying a WIX.
This filter is significantly different from the others in that the media cartridge is much shorter than the stock Suzuki filter (7mm less), and that makes for at least 16% less surface area, but to make matters worse, the pleats are spaced further apart, again reducing total surface area. We calculate that the total surface area is reduced by at least 20% under the stock Suzuki filter for the same engine, and that does not give us much confidence. The CARQUEST / WIX filter does have the anti-drain back valve and an interesting version of an overpressure valve which is located near the base plate. The overpressure valve also seems to work as an adapter of sorts to the media canister, but there is only loose fitting, metal to metal contact between the bypass surfaces and the pleated media end cap which, without a seal, would likely leak under pressure allowing contaminated oil to pass by. 
The WIX website does claim the filter media is “prescription blended” of a combination cellulose/fiberglass media capable of stopping particles 25 microns and larger. (Not an overly impressive claim.) However, they also reference the SAE testing method which has been replaced with the more current and internationally recognized ISO 4548-12 method. Perhaps other CARQUEST / WIX filters for other models are constructed differently, but we cannot recommend this one for the Suzuki KingQuad. Without cutting open a WIX filter for every model, we have to assume this design is common to many of their filters, and with much better choices available, we’ll leave the WIX / CARQUEST on the shelf.
K & N – K & N knows performance and they are a highly respected brand in the ATV, motorcycle, and off-road aftermarket. K & N oil filters are made of a fully synthetic media allowing them to trap a claimed 99% of all harmful particles 10-20 microns and larger at a higher flow rate than the standard OEM filter. This is possible not only because of the filter media, but also because the pleats in the K & N filter are oriented differently. As a result the K & N filter easily surpasses all O.E.M. specs. Anti-drain back and overpressure valves are standard, but one of the features we like best is the 17mm nut spot welded to the end of the canister which makes them a LOT easier to remove or install, especially in tight quarters. Since K & N is also highly involved with racing, they even include a safety wire attachment to keep it from backing off under brutal racing conditions, and as mandated by some sanctioning bodies. We’ve never had a K&N product let us down. 
FRAM – The FRAM name is to oil filters as Trojan is to... well, you know. Oddly enough, both are protection devices working on a similar principle. There is a lot to like about the FRAM filter beginning with the grippy coating on the end of the canister that helps you remove or install it. Inside is where the critical parts come together though. The FRAM filter features a cellulose/synthetic blend media that will stop particles 20 microns and larger, and the flow rate, dirt trapping capability, and surface area are all designed to surpass the OEM filter. The FRAM filters also feature an anti-drain back valve at the bottom and a cold start/overpressure bypass valve at the top. Interestingly, instead of metal end caps on the filter media, FRAM uses fiberboard caps that are glued and sealed. Some take exception to the fiberboard end cap preferring a metal end cap for added rigidity, durability, and protection. Nonetheless, whatever the end cap material is made from, as long as it is sealed, it will work. In fact, Toyota simply glues the end of the filter media on some of their filters. We have confidence in this filter. 
Choose Wisely
After our dissection and discovery session, we believe the K & N filters are superior in nearly every way, followed by the FRAM. The filter media is excellent both in size and dirt stopping capability, they offer protection for cold start conditions thanks to both the anti-drain back and bypass valves, and they even include a feature to make them easier to install or remove. Our next pick would be the OEM filter, followed closely by the EMGO, both of which are extremely similar but of unknown media composition or capabilities. Let’s face it; there are a lot of EMGO products that we have questions about. Finally, because of the greatly reduced surface area, and a bypass system that leaves a very loose fit at all times, the WIX / CARQUEST filter is the last we would install. It’s simply not on par with the others, at least in this case. Your engine is definitely worth a whole lot more than any perceived savings from bargain basement filters.
The oil and oil filter you choose are critical to engine performance and durability. It’s not the time to skimp on quality. Luckily, the premium filters we prefer are less costly than the OEM filter, which is generally the most expensive of the group! If the parts guy at the dealership gets lonely, hook him up with the lady at the bank.
