Oil Filter Tests

Oil filter tests determines the actual filtration performance of an oil filter. A quality oil filter has the ability to improve engine longevity, increase maintenance intervals, and result in substantial financial savings over the life of a vehicle. But when choosing an oil filter, how does a consumer determine which filter actually performs the best? For some insight, let’s examine how the industry tests oil filters.

All car oil filters have to undergo SAE (Society of Automotive Engineers) tests if they are to be considered in compliance with the vehicle manufacturer's specifications. There are two tests available for automobile engine oil filters. All automotive oil filters sold in the United States are only required to pass a simple single-pass test from the Society of Automotive Engineers (SAE) with only a simple pass or fail score. One of the original oil filtering tests was the SAE HS806 test. The SAE HS806 test uses a single-pass test, checking for contaminant holding capacity, size of contaminant particles trapped, and ability to maintain clean oil. The original nominal test was quite crude and simple in nature with just a single pass of dirty engine oil going through the filter. In order to pass the SAE HS806 test, just a minimum filtering threshold needed to be met.

Later, various amendments were issued to the SAE HS806 test. These included a multi-pass test that determines the filter’s expected filtering life, which was measured in hours. The oil filters expected filtering life was determined by subjecting the filter to a standard contaminate particle size carried in a given weight of motor oil at a constant flow rate, pressure and temperature. The test continued until the filtering media became clogged enough to raise the differential pressure drop across the oil filters intake and exit port to the predetermined level. After the oil filters filtering ability declined and fell under the standard level, the filter was then weighed and the gravimetric measurement of the filtered test oil was subtracted from the finishing weight, which resulted in the total weight of contaminant that the filter could effectively hold. The efficiency of the filter is determined only by weight through gravimetric measurement of the filtered test liquid. Typical numbers for paper filter elements are around 85% (single pass) and 80% (multi-pass).
Due to the above testing parameters, the life and efficiency test results generally include a time weight efficiency measurement, which is, was usually stated as a percentage, and total holding capacity stated in a unit of grams.
Due to the shortfalls in the HS806 filtering testing, the SAE decided to create a new an advanced optional filtering standard called J1858.

The SAE J1858 is a superior beta ratio test that is optional to the oil filter manufacturers that feel that the standard SAE HS806 test is too lax. The beta ratio test is defined as the ratio of the total number of particles upstream of the oil filter verse the total number of particles downstream of the oil filter for a predetermined determined particle size.

The new testing procedure is also no longer a simple one-pass test like the HS806 test. The J1858 test counts the size and quantity of the particles entering and leaving the oil filter and is a multiple pass test. Multiple pass testing is considered the most efficient way of testing oil filters, as it is similar to the operation of the oil filter on the vehicle. Multiple pass testing procedures have been recognized by SAE (SAE J1858), ISO (ISO 4548-12, engine lubricating oil and ISO16889, hydraulic or fuel), ANSI (American National Standards Institute) and NFPA (National Fluid Power Association).


The new test provides both gravimetric measurement and particle counting to measure both the micron filtering capacity of the oil filter as well as the total filtering capacity of the oil filter. Actual counts of contaminant particles by size are obtained every 10 minutes, both upstream (before the filter) and downstream (after the filter), for evaluation using lasers to detect the size and quantity of the particles entering and leaving the oil filter. This determines the beta ratio.
Using the beta ratio test, the filtering capacity of the oil filter with a beta rating of 85 at a 15 micron particle size will have a mean of 85 separate particles that are 15 microns in size upstream of the oil filter for every single 15 micron particle down stream of the oil filter. The flow rates through the oil filter can also very from 0.5 to 60 gallons per minuet. The change in flow rate of the oil through the filter is necessary in order to replicate the engines true operating conditions. These operating parameters can start from the initial cranking of the engine, which would result in a large spike in oil pressure with a low volume of oil flow, to full throttle, where the flow rate and pressure would be at there maximum.

From this data, filtration ratio and efficiency for each contaminant particle size can be determined as well as dust capacity and pressure loss as a function of time.


All filters must be tested with the J806 test, but the new J1858 is much more meaningful. Currently, the J1858 test is optional. Usually, the high-end filter manufacturers are the most anxious to display these numbers.

Most automotive oil filters state their efficiency rating in a micron filtering number. Microns are a linear measurement indicating length, or in relation to automotive oil filters, it indicates the length and width of various particle sizes. Micron ratings are some what of an arbitrary number as it only indicates the oil filters ability to remove contaminants at a particular particle size and not the efficiency or total contaminant holding capacity of the oil filter. What does the word micron mean? The word micron is another term for micrometer (1 millionth of a meter). A simple comparison is that a 25-micron particle is approximately 0.001 of an inch. Some linear equivalents are 1 inch is 25,400microns and 1 micron is .000039 inches.


Some comparative sizes are:

Diameter of average human hair 70 microns
Lower limit of visibility (naked eye) 40 microns
White blood cells 25 microns
Talcum powder 10 microns
Red blood cells 8 microns
Bacteria 2 microns
Carbon black 0.6 microns
Tobacco smoke 0.5 microns

Typical numbers for paper element filters are 40% efficiency at 10 microns, 60% at 20 microns, 93% at 30 microns, and 97% at 40 microns.

A filter that is marked or rated "10 micron" has some capability to capture particles as small as 10 micrometers. However, when you see a filter marked "10 micron", you do not know exactly what this means unless you also have a description of the test methods and standards used to determine the filter rating. The results from the different test methods may not be comparable as their methodology varies greatly.

Many automotive filtering companies state that their oil filters can filter down to 10 microns or 0.00033 of an inch, but at what percentage can they filter that size of a particle. Stating an oil filters micron rating without stating the filtering efficiency and capacity at that particle size is misleading. For example, all automotive oil filters will filter a 10-micron particle to some extent. Some cheaper designs will only filter one percent of all 10-micron particles in the engine oil, while others can filter out 75 percent of all 10 microns particles. The difference between a mediocre and superior oil filter design is that the poor design will only filter the 10 micron particle by chance, while the superior oil filter was designed to specifically filter 75 percent of all 10 micron particles.

The main advantage of the new SAE J1858 test is that the filtering ratio and efficiency for varying sizes of particles and the pressure drop across the filter as a function of time can be determined. Compared to the standard SAE HS806 test, the SAE J1858 test does a far better job in determining the total filtering capacity of the oil filter, actual filtering percentage values at various micron ratings, and the differential pressure capabilities. But, the J1858 test is by no means perfect.

First, the J1858 test was only an optional test that the majority of automotive oil filter makers did not use. Then, there are two basic testing options for companies that undergo the optional SAE J1858 test. First, the companies can have the oil filter name stated with their test results that are published by the SAE in their journals and or publish the filtering specifications in their advertisement. But, the manufactures can also simply state in their advertising that they passed the test, but not state the oil filter’s test results.


Another problem is that the test results were not required by the SAE to be published using the filters name, make and model. The oil filter manufactures can request that the filtering data be considered proprietary information, which results in no one but the manufacturer knowing the testing results. Unfortunately, keeping the test results proprietary is the most common approach used by the oil filter companies.

Again, this results in customers not knowing the filtering capacities of the each oil filter that passed the J1858 test, and only knowing that they met the minimum J1858 cut off point. This again limits the customer’s ability to determine whom makes the best automotive oil filter and which filter best suits their individual needs.

So, what is the bottom line? How does a consumer make an educated choice? You must do your homework and decide for yourself. Though accurate information on individual oil filter testing is difficult to obtain, perhaps one way to research the matter is through the filter manufacturers themselves, through their publications and websites. While each manufacturer will certainly extol the virtues of their own product, the better the product, the more likely the manufacturer is to disclose the details. If the oil filter testing information you want isn’t readily available, there is probably a reason; either it doesn’t exist, or the manufacturer isn’t proud of it.

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