Having cleaner oil is better for the reliability of the engine. ⁶⁾
There’s an old saying that oil doesn’t wear out; it just gets dirty.
Although there is some validity to the idea that dirtier oil will “age” quicker than clean oil,
The engine oil will have a finite life. It will need to be changed eventually no matter how clean you keep it.

• Filter ratings are the most often misunderstood area of contamination control. ⁷⁾
  • A nominal rating is an arbitrary size value assigned to a filter by the manufacturer.
  • Tests have shown that particles as large as 200 microns will pass through a nominally rated 10-micron filter.
  • Because the nominal rating is arbitrary, it has no value.

Often limited by physical size, engine oil filters are relatively small when compared to their industrial counterparts. ⁸⁾
This small size coincides with less filter media surface area through which to pass the lubricant.

Look for the inside diameter threading listed in the filter specs.

• Different vehicle manufacturers use either a metric (20mm) or a standard (3/4“-16) threaded filter mounting adapter.
  (the threaded spud that holds the filter onto the engine) ⁹⁾
  • It is very important that the oil filter adapter size be verified prior to buying / installing a replacement oil filter on your bike.
  • Using a metric threaded filter on the standard threaded mounting adapter will result in loss of oil and possible engine damage.
  • You can carefully test fit an open ended wrench on the threads on the filter pad.
    1. Drain the oil and remove the existing filter.
    2. Using a quality 3/4” open-end wrench, try to slip the open end of the wrench over the adapter threads.
    3. If the 3/4” wrench fits around the threads, the thread size is 3/4“-16.
    4. If the 3/4” wrench does not fit over the threads, the thread size is 20mm.

In a case study performed by General Motors and published by the Society of Automotive Engineers (SAE);
It was determined that engine service life could be extended eight times when 5-micron filtration is implemented vs. the standard 40-micron filtration. ¹⁰⁾

• The oil filter media is the actual material used to capture contaminants in a filter element. ¹¹⁾
  • Whatever media is used, it usually starts out in sheet form and is then folded or pleated to expose more surface area to oil flow.
  • This is done to increase contaminant carrying capacity and to reduce the pressure differential across the filter.
• The most common media: ¹²⁾
  • Wire mesh: constructed of either standard or stainless steel in a woven mesh.
    Because of the limitations in wire size and construction techniques, they are not available in very fine micron ratings.
  • Cellulose: made from wood pulp.
    The “paper” used for cellulose filters isn’t much more sophisticated than the paper used for writing.
    They are however cheap.
    The downside of this type of media is that it is not very efficient nor do they have a high dirt holding capacity. Cellulose also absorbs water, which may or may not be a benefit.
    They can be used to remove water from the system, however if this is not the desired effect and there is water in the system, the filter element will still absorb water.
    The pressure differential will increase and the filter will appear clogged.
  • Fiberglass: a type of synthetic filter media.
    In general, synthetic media performs considerably better than cellulose media because the fibers can be manufactured in a more uniform size distribution and thinner than cellulose media.
    Multiple layers of differing quality can be used to create a medium that is both extremely efficient and offers great dirt holding capacity.

• The media pore size is the major determinant in how efficient and how small of particles the filter can remove. ¹³⁾
  • The physical size of the filter is usually determined by the other components around it.
    The flow rate must be high enough to feed all the lubricated components.
    This means you can’t make the pore size too small or it will raise the pressure differential and the bypass valve will open, effectively rendering the filter useless.
  • In a case study performed by General Motors and published by the Society of Automotive Engineers (SAE);
    It was determined that engine service life could be extended eight times when 5-micron filtration is implemented vs. the standard 40-micron filtration.

• A micron is another name for micro-meter. (1 millionth of a meter or 39 millionths of an inch).
• Micron ratings were used initially by various filter manufacturers to evaluate the relating porosity of flat sheets of media used in making filter elements.
  (intended purpose to indicate the relative freeness or tightness of a sheet of filter media)
  

• However, the micron rating is also now falsely used as a widespread measure of filtration efficiency.
  (unintended purpose)
  Here are some of the reasons why a micron rating is totally inappropriate for this use: ¹⁴⁾
  1. The test is not repeatable at different labs.
     • Each manufacturer has its own test procedures.
     • Although the test is a valid comparison of one paper to another within a given company,
     • The micron rating does not lend comparison of filters made by different manufacturers.
     • While one manufacturer may give a paper a nominal micron rating of 10,
     • Another may rate it a 2.
     • A third manufacturer may rate the same paper a 15.
     • There is no across the board basis for comparison.
  2. There is no consistent relationship between micron rating and actual filtration efficiency.
     • The relative porosity of a sheet of filter media is only one of the factors which determines the efficiency of a filter.
     • The physical construction of the media, filter, element and the types of contaminants to be encountered, are also very important factors.
     • The entire filter needs to be tested, not just the paper.
  3. The micron rating does not show what happens to a filter over time.
     • The performance of a liquid filter may deteriorate with use.
     • The micron rating is a one-pass test done on a new sample of filter paper.
       (which provides no information about how a filter will stand up under continued use)
     • The inadequacies of micron ratings have been readily apparent to the vast majority of OEMs.
• Changes in testing procedures may eventually come around.
  • Many have established their own rigid, repeatable, performance criteria which a filter must meet to qualify as acceptable for a particular vehicle.
  • Others are calling for the standardized multi-pass test and its resultant unit of measure (the B ratio).
    • SAE is currently moving toward adopting the multi-pass test as a standard procedure.
  • Unfortunately, reliance on micron ratings is still wide-spread at the user level.
  • Filter manufacturers reluctantly provide micron ratings to fleets who are still insistent on having this information.
    (even though it serves more to confuse than to clarify)

• The pressure differential is the change in pressure from the inlet to the outlet side of the filter. ¹⁵⁾
  • If the pressure differential is too high, a valve will open, allowing the oil to bypass the filter.
  • All engine oil filters or heads are equipped with a bypass valve.
  • This valve is needed so the engine does not become starved of oil as the filter clogs with debris.
• The higher the bypass pressure setting, the more oil is forced through the filter. ¹⁶⁾
• In a full flow oil system, all the oil passes through the filter to reach the engine. ¹⁷⁾

• If the filter clogs, an alternative route to the engine must be provided for the oil.
  (or the bearings and other internal parts may fail due to oil starvation)
• A relief (or bypass) valve is used to allow unfiltered oil to lubricate the engine.
  • Unfiltered oil is far better than no oil at all.
• This relief valve is built into some engine cases.
• Otherwise, the relief valve is a component of the oil filter itself.
• Under normal conditions, the valve remains closed.
• When there is sufficient contaminant in the oil filter to reach a preset level of restriction to oil flow,
  • The pressure on the relief valve causes it to open.
• This condition can occur when the oil filter has become clogged or when the weather is cold and the oil is thick and flows slowly.

• Some oil filter mountings may allow oil to drain out of the filter when the engine is stopped. ¹⁸⁾
  • When the engine is next started, oil must refill the filter before full oil pressure reaches the engine.
  • The anti-drain valve (included in some filters) prevents oil from draining out of the filter.
  • Some filter designs incorporate a combination anti-drain and relief valve with an integrated

unit construction.