AMSOIL 2-Stage Air Foam Air Filter outperforms both high quality paper filter, low quality paper filters and oil-wetted gauze (K&N) in the SAE J726C Test Method which tests for air flow, dirt removal and filter life.

Dirt is your engine's worst enemy! The only thing stopping abrasive airborne dirt and grit from entering and seriously damaging your engine is your air filter. But in order to do the job right, and air filter must not only effectively stop harmful dirt, it must do so without obstructing the vital flow of air that allows proper combustion and maximum engine performance.

This website page describes the air filter test equipment we have and how various types of air filter sections perform when tested on this machine.

For example, one manufacturer of oil-wetted gauze filters (K&N) claims their filters are superior, but our test machine shows that they do not stop the small dirt particles as well as oiled foam filters do.

The air filter test machine consists of a three inch diameter clear plastic PVC tube coupled to a vacuum motor. The top of the tube has an aluminum mounting plate for air filter sections and the bottom of the tube has a place to install an oiled piece of white foam pad to prevent dirt particles from being sucked into the motor and destroying it.

A 5 x 5 inch. section of a freshly oiled air filter is placed on the mounting plate and secured. The test machine is turned on and one teaspoon of Standardized Air Filter Testing Dust is sprinkled on the top of the filter section. The machine is then shut off and the filter section and pvc tube is removed in order to inspect the white oiled foam pad. In each test of a oil-wetted gauze filter test (K&N), the oiled foam is gritty and full of test dust particles as is the inside of the PVC tube. A paper air filter also lets the test dirt through but varies depending on the quality of the paper filter.

When the exact same test is replicated with a section of an AMSOIL 2-Stage Foam Air Filter using an entire bag of test dust there is absolutely no test dust particles on the oiled foam.

If the same test is run again, only this time lightly tapping the top of the filters, simulating vehicle impacts and vibrations, the test dust ingress is even worse for the oil-wetted gauze (K&N) while with the AMSOIL foam filter there is still no test dust particles on the foam.

This test shows how oil-wetted gauze and paper air filters do not stop dirt particles as well as an AMSOIL Two-Stage foam filter does. Sure, they may flow air very well on a flowbench, dynomometer and in high performance applications, but what good is all the airflow if the filter isn't trapping and holding all the abrasive dirt particles?

Additionally, take a look at the oil used on the oil-wetted gauze filters. It is a lightweight viscosity spray oil. Put it between your index finger and your thumb and pull them apart and you'll see that nothing happens. In contrast, try the same thing with AMSOIL Foam Air Filter Oil, which has a very high viscosity and when you pull your fingers apart the oil stretches because of it's extremely high tack properties. This is what you need on a filter to stop dirt dead in its tracks.

Same thing goes for other manufactures of foam air filters, like UNI, for example. They also make an excellent foam air filter and use a very high tack oil. Fact is, there is absolutely no better air filtration media than oiled foam. Take a look at every off-road motorcycle that is used in extremely dusty environments. They all have oiled foam air filters!

We have received numerous questions and concerns from K&N filter users with the Dodge Cummins Turbodiesel and the Ford Powerstroke Diesel asking why the air filter restriction gauge never moves when using a K&N air filter. The answer is that the K&N has higher airflow capability due to larger holes in the filtering media and it does not stop enough dirt particles to ever make the filter become restricted enough to make the restriction gauge move. Take the K&N out and put in a paper filter an eventually the paper filter will trap enough dirt that the restriction gauge will move. Same thing with the AMSOIL foam air filter: as it traps dirt, eventually it will cause the gauge to move, but it will take a longer period of time due to it's superior filtering AND airflow capabilities. This same issue was addressed in the Q&A section of a recent issue of the Turbo Diesel Register magazine.

We have no issue with oil-wetted gauze filters (K&N) other than our test equipment indicates that their filters don't stop all the small dirt particles. They do flow air well, but what good is all the airflow if the filter isn't trapping and holding all the dirt particles?

So, you may then ask why do so many race cars use oil-wetted gauze filters? Our response is they are interested in airflow and horsepower. Racing engines get disassembled, inspected and re-built at least once a season and in many cases several times a season therefore dirt stopping ability is not the primary concern. And, where dirt stopping ability is a concern, such as off-road racing, one manufacturer of oil-wetted gauze (K&N) offers a foam wrap as described below.

An advertisement in the new products section of a performance racing publication shows that K&N has released an open cell K&N Airforce Precleaner for their 14 inch diameter round filters. It is an open cell foam wrap with a special oil. The heading on their advertisement says: "Keep 90% of the Dirt Out". We say, ok great. Now, what about the rest of the K&N's for everyday car and truck use? Don't they also need a foam wrap?

Our Conclusion is just as we stated previously: There is absolutely no better filtering media than oiled foam.

The AMSOIL 2-Stage Air Filter is a maximum performance, extended life filter that combines the very best possible filtration with better air flow characteristics. Its two thick layers of oiled polyurethane foam allow air to pass through virtually unrestricted, while stopping and holding destructive dirt and grit.

The AMSOIL 2-Stage Foam Air Filter is the best form of insurance that you can buy for your engine. Its washable and reusable design provides many thousands of miles of trouble-free service. The AMSOIL 2-Stage Filter is designed to last indefinitely with proper service. Under normal driving conditions, it may be used for 25,000 miles or one year between cleaning and servicing. Under dusty driving conditions, it should be cleaned and serviced more frequently.

Here's a more detailed test procedure and conclusive results covering AMSOIL vs. K&N and paper air filters according to the Industry Standard Society of Automotive Engineers (SAE) test standard SAE J726.

Your car's engine "inhales" air that is mixed with fuel for combustion. But air contains an incredible amount of suspended dirt - typically 400 tons of it in a cubic mile. Much of this is microscopic dirt, extremely abrasive, that can cause serious damage inside the engine. Consequently, an air filter is a

An air cleaner must not only trap as much grit as possible, but it should do so without "smothering" the engine, restricting its vital airflow. Thus the most desirable performance characteristics for an air cleaning device are high dirt-trapping efficiency, and minimal airflow restriction as the dirt accumulates.

The Society of Automotive Engineers Test Code J726 specifies the procedures, conditions, equipment, and report format which air filters can be uniformly compared. A standardized dust contaminant is introduced into a specially designed testing apparatus at a controlled rate. Most of the dust will be trapped in the filter undergoing the test; the remainder is captured in an "absolute filter".

The air pressure upstream and downstream of the test unit is monitored. The test terminates when the pressure differential causes a predetermined amount of fluid displacement on a water manometer. By quantifying and comparing weights, pressures, and elapsed time, the experimenter can determine a filters efficiency, capacity and airflow-based life expectancy.

Our J726 trials were conducted at an independent testing facility in the upper midwest. The tests compared Motorvator, K&N, Accel, Fram, and AMSOIL products. The results? AMSOIL proved vastly superior to the competitors' air cleaners as the only air filter to consistently score high marks in all three vital areas of airflow, efficiency and capacity.

The AMSOIL 2-Stage Air Filter traps airborne dust with 99% efficiency; it holds an incredible 281 grams of contaminant (that's over half a pound); and it outlasts the competition. It performs two to four times longer than the others. That's why AMSOIL can confidently recommend a 25,000 mile/1-year service life. And the 2-Stage is actually re-usable, with proper cleaning and re-oiling.

How does AMSOIL do it? Two different densities of lightly oiled polyurethane foam surrounding an expanded metal cage, precisely assembled by careful craftsman in AMSOIL's own manufacturing plant- that's how!