Oil Filtration Facts!
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Useful oil filtration information is presented here to help you make an
informed decision regarding your choice of filtration products for your vehicles and equipment.
One of the most important items involved in achieving maximum longevity and optimum performance from an engine is in how well the oil, air and fuel is filtered. The primary objective of an oil filter is to eliminate the maximum quantity of abrasive particles. If these particles are not effectively filtered out, the life cycle of the engine will be drastically reduced.
The job of an oil filter is to remove atmospheric contaminants, wear particulates caused during engine operation and particulates in the oil created during the combustion process. The sum of these contaminants, if not properly filtered, can wreak havoc on an engine and drastically reduce its longevity. These particulates include products from fuel and its components such as carbon caused by the transfer of combustion products from the fuel to the crankcase oil.
Carbon and soot is the cause of many deposits found inside engines. Diesel engines, in particular, can have very high degrees of carbon and soot build up, especially if they are operating with a plugged air filter and under heavy load, since the quantity of air is drastically reduced. Although air filtration is extremely important, whether the engine is operating on gasoline or diesel fuel, diesel engines consume much more air during operation than gasoline engines. Other deposits can be caused by oil diluted with fuel from poor combustion or from an improperly warmed engine where unburned fuel can blow by the piston rings and enter the crankcase.
The engine wearing during use also causes deposits. The resultant products of this type of wear include iron, lead, copper, tin, aluminum from bearing and bushing material and other metals such as chromium from piston rings and valve train parts. Other significant sources of engine oil contamination include silicon left inside the block from sand casting at the foundry, machining particles from manufacturing and certain coolants and additives and particulates introduced from faulty or worn sealing surfaces, especially seals such as front and rear crankshaft and water pump seals, gasket materials or sealants.
Another often-overlooked area of particulate entry is the funnel or oil container itself. Oil containers are sealed at the factory but after opening one it is easy for dirt particles to accumulate around the opening or in the funnel used to direct the unfiltered oil into the engine.
As a side note, you may wonder why sand from machining operations at the factory is not fully cleaned out during the preparation and assembly process. The manufacturer does attempt to get all casting and machining particles out, but still, the fact remains that there are millions of microscopic peaks and valleys and surfaces and passageways inside a cast surface that these microscopic particles of sand and metals may become embedded and are not all cleaned out during the wash process.
The most effective way to clean cast surfaces is with hot steam, water and an industrial soap solution. That’s why when rebuilding an engine after machining the cylinders, regardless of how well you clean them with parts cleaner, carburetor cleaner, brake cleaner, etc., the most effective method is to use warm dish soap and water to thoroughly clean all machined surfaces. Then after cleaning, rub lightweight oil on the parts to prevent the humidity in the air from causing corrosion.
The fact is, that even with modern manufacturing practices, there is still a certain amount of unfiltered abrasives inside an engine from the manufacturing or rebuilding process. That is why filtration is so critical. In the absence of proper oil filtration, these particles can be picked up and carried into circulation. One single particle embedded in a bearing is capable of causing appreciable damage.
The Effect of Used Oil Contaminants on Engine Wear
The role of oil filters is, firstly, to remove all abrasive particles larger than a certain size, thus establishing a certain degree of oil filtration (more on this later). Given that general clearances between crankshaft and connecting rod bearings in modern automotive engines is between 0.0006-0.002 in. (15-50 microns) up to 0.003-0.004 in. (80-100 microns) in certain large industrial or diesel engines, and the thickness of oil film is between 5 and 75 microns with no load and 5 to 15 microns when fully loaded.
Steps should be taken to remove all hard particles with a diameter of more than 5 microns or, at least, those between 10 and 15 microns in diameter. This does not mean that smaller particles do not have any effect on wear. These non-filtered size limits are also shown by numerous engine tests with dust particles of different sizes introduced into the crankcase oil.
The test results show that:
Abrasive particles between 0 and 5 microns cause significant wear.
The wear of all engine parts does not reach a maximum value for the same particle size.
Wear of cylinder and rings reaches a maximum value with a smaller particle size than that causing maximum bearing wear. This appears to be due to the differences in clearances of these parts during running and also to the relative hardness of the metals used.
Tests, using a diesel engine fitted with a radioactive top ring, illustrates the distribution of the size of metallic particles caused by actual ring wear during running:
55% of particles have a diameter of less than 8 microns.
28% of particles have a diameter of less than 5 microns.
7% of particles have a diameter of less than 1.2 microns.
0.5% of particles have a diameter of less than 0.45 microns.
These findings show that the metallic particles scraped off an engine play an appreciable role in the process of engine wear, merely on account of their size. The finest particles, i.e. those between 0 and 5 microns and accounting for 28% of the total particles present, mainly have an abrasive and erosive effect on wear in the upper part of an engine (cylinders and rings), whereas 45% of the unfiltered particles larger than 8 microns in diameter tend to act on the lower parts (bearings).
It is only through repeated passages of the oil through the oil filter that filtration is complete. A standard automobile engine filter, fitted to a full-flow oil circuit, shows a certain amount of dust passing the filter in its first passage through, i.e., 25% of particles between 10 and 20 microns, 15% between 0 and 10 microns, and 2% from 60 to 100 microns. It is the particles between 10 and 20 microns that are the most dangerous for engine wear and which must be removed as quickly as possible. The use of a second filter, or filtering in stages, may be useful provided the variation of load drop with time remains reasonable.
Oil Filters And Oil Filtration Systems
There are two types of oil filter elements and two types of oil filtration systems. These are surface oil filter elements, depth type oil filter elements and full flow and by-pass filtration systems.
Surface Type Oil Filter Elements
Surface type oil filter elements are the most common. In this type of oil filtration, system oil passes through only one layer of filtering media. This media is typically some form of pleated paper, paper-synthetic media or paper-fiberglass or a fully synthetic or fiberglass media. The paper is often treated with impregnants such as phenol resins and the impregnation is polymerized and the paper silicon treated. The purpose of this treatment is to increase the mechanical resistance of the paper, to even out channel patterns and to provide greater resistance under the corrosive effects of the oil.
The object of a pleated type surface element is to achieve maximum surface area inside a minimum volume. The specific pore size of the element is what determines the filters micron rating. However, the micron rating of a filter can be very deceptive. The general range of particle sizes that a surface type filter will stop is in the 10-40 micron range. The critical parameter is not what particle sizes a filter traps, but at what efficiency it captures those particular particles (i.e., particle capture percentage).
Be very cautious of full flow oil filters advertising a certain micron rating as a main selling point unless it also specifically states what efficiency it achieves at that micron size or shows a graph indicating the efficiency at various micron sizes. For example, a screen door could be stated to stop 1 micron particles from passing through, yet the percentage of the total 1 micron particles that a screen door will stop is going to be extremely small, and pretty close to zero.
Surface type oil filters are normally mounted in full flow applications, meaning that all of the lubricant in the circuit passes through the filter, but not necessarily through the media. This is due to the action of the bypass valve, which opens under certain circumstances (cold start-ups or pressure surges) and allows an uninterrupted flow of unfiltered oil while the valve is open. Another instance where the bypass valve will open is when a filter is filled to its maximum with particulates, in which case unfiltered oil will be flowing to the engine.
Some surface type filters on the market are advertised as “10 micron” filters, for example. However, nowhere on the box does it state the efficiency rating. Thus the “10 micron” value advertised is totally useless, and probably, deceptive to the end user who may think they are actually getting a filter that stops all 10 micron particles. As an example, testing, conducted at the Milwaukee School of Engineering; Fluid Power Institute using SAE Test Method J806 for filtration efficiency, indicates the following at the lower efficiency end of the graph.
Fram PH8A oil filter is 10% efficient a trapping 12 micron particles.
AC PF-2 oil filter is 10% efficient at trapping 4.5 micron particles.
Purolator PER-1 oil filter is 10% efficient at trapping14 micron particles.
Ford FL-1 oil filter is 10% efficient at trapping12 micron particles.
At the upper efficiency range of the graph:
Fram PH8A is 78% efficient at removing 20 micron particles.
AC PF-2 is 67% efficient at trapping 20 micron particles.
Purolator PER-1 is 42% efficient at trapping 20 micron particles.
Ford Fl-1 is 33% efficient at trapping 20 micron particles.
This test serves to show the wide variation in particle capture percentages for some common oil filters. The test also illustrates that the size range in which 60% of engine wear occurs is in the 5 to 20 micron range. This indicates that, in general, surface type flow oil filters are not very efficient at filtering out the particles that cause 60 % of engine wear. There are premium quality surface type full flow filters on the market that will outperform the filters used in this test. This also illustrates the need for by-pass oil filtration, which will be covered later. Note that in the same test, a by-pass oil filter manufactured by AMSOIL INC. filtered out 100% of the 5-20 micron particles and about 85% of the 1 micron particles. The AMSOIL Super Duty full flow oil filter is approximately 65% efficient at filtering 15-micron particles. This is exceptional for a full flow oil filter.
The Beta rating of an oil filter is a measure of the particle capture percentage in a special test designed and specified by the Society of Automotive Engineers (SAE) and is referred to as test SAE J1858. The test measures the volume of particles that pass through a filter in a single pass vs. the total volume of particles introduced into the filtration system prior to entering the oil filter. The percent efficiency of a filter with a specific beta rating is determined by subtracting one from the Beta rating, then divide the result by the actual Beta rating and multiplying the result of the division by 100. The final value determines exactly how efficient a certain oil filter is at removing a specific size of contaminant.
Beta rating tests are the best way to accurately compare oil filter performance due to the fact that the test measures the specific oil filter’s efficiencies at specific particle sizes. Comparing filter micron ratings without knowing the efficiency at a specific micron particle size is meaningless.
Depth Type Oil Filter Elements
Depth type oil filters have elements that are constructed of materials that are referred to as “absorbent” and these consist of inactive materials such as cotton waste, waste paper, wound paper, cellulose, cloth, wood pulp, asbestos, etc., which are tightly packed together. These types of filters depend on the absorption of contaminants as the oil flows through the media.
It takes quite a while for the oil to flow through a depth type oil filter. That is the reason that depth type oil filters are plumbed into an oil system as a secondary, or by-pass, oil filter. If they were plumbed into the full flow system, the oil would take too long to flow through and the engine would not receive sufficient quantities of oil volume. Depth type filters typically do not have bypass valves since they are not plumbed into the full flow oil system. If a depth type oil filter plumbed in a system as a bypass filter became plugged, the full flow oil filter would remain functional.
Many poorly constructed absorbent depth filters are susceptible to a condition called channeling. Channeling is a condition whereby the oil flow through the media creates a “channel” or locates a path of least resistance. Once channeling occurs, effective filtration ceases.
Depth type absorbent filters will not remove oil additives (unless the additive is a solid lubricant such as graphite and the particle size is in the size range which may prevent them from moving through the filter).
Another group of materials used in some depth type filters are referred to as “adsorbent” and consist of chemically active materials such as Fullers earth, clays, charcoal and chemically treated paper. These filters remove contaminants through a chemical reaction with the lubricant, and as a result, may remove some oil additives.
Adsorbent type depth filters are not recommend since they cannot selectively filter out only the harmful materials and in the process may filter out necessary additives that were engineered into the oil by the oil manufacturer.
Full Flow Oil Filtration Systems
Full flow oil filtration is the type that is used on almost every major automobile and light truck in production, as well as many other medium and heavy-duty trucks. In a full flow system, all of the oil from the oil pump must pass through the oil filter. Filters used in this type of system must have a high degree of single-pass efficiency and a low restriction to oil flow. What this means is that the filter must be effective at removing engine damaging particulates from the engine oil the first time it passes through the oil filter for good oil filtration.
In order to ensure that the engine is properly lubricated under all operating conditions, and if the filter becomes plugged, a bypass valve is engineered into the oil filter, or on some vehicles, a pressure-regulating valve is designed into the engine lubrication system, so one is not necessary in the filter. The bypass valve is closed under normal operating conditions. But, if the filter becomes plugged, the valve will open and supply unfiltered oil directly to the engine. This will prevent engine damage due to lack of oil flow, but it is not good to have unfiltered oil flowing to the engine, although still much better than the alternative of oil starvation and certain engine failure.
It is very important that you use the oil filter type (not brand) specified by the engine manufacturer as each filter has different bypass valve pressure ratings which correspond to the specific engine it is to be used on.
Full-flow filters install directly into the line of oil circulation. The full flow of oil passes through the filter as the oil journeys between the oil pump and engine. A full flow filter must be capable of removing and holding contaminants without obstructing oil flow to the engine.
Most conventional filters on the market use a thin layer of porous filter paper as their filtration media, which compromises their ability to catch fine particles. In addition, these filters have almost no extended cleaning ability since their media have a low capacity for storing dirt.
Because of their limited filtering area, most conventional paper filters display good flow characteristics but are restricted in their capacity and longevity. They become obstructed relatively quickly, opening the relief valve and allowing unfiltered oil into the engine. Their lightweight construction also makes them susceptible to degradation.
By-pass Oil Filtration Systems
By-pass oil filtration systems typically take only a very small percentage of the oil (usually about 10% or less) of the oil flow from the pump. The most common location to tap into is at the oil-pressure sending unit by utilizing a special tee fitting. There are several types of by-pass systems but, in general, the simplest type of by-pass filter systems are the type that have a remote mounted depth type filter on a small valve block. The valve block has metering valves and orifices in it in order to only allow a small portion, usually about 10%, of the oil to flow through it at any given time.
The depth type filter is designed in such a way as to “super-filter” the oil and thus it takes longer for the oil to flow through the filter. The filtered oil is returned to either the oil pan, valve cover or filler cap via a special fitting. The hydraulic line used for this type of installation is generally ¼ inch inside diameter.
By-pass systems on heavy diesel engines are installed differently. These engines come from the manufacturer with special ports in the engine block and oil pan specifically for this purpose. Once it is determined which port is pressure and which is for the return oil, it is simply a matter of using the proper threaded fittings to adapt to the ports and by-pass system valve block.
Some oil pans come with a threaded port for returning filtered oil and some do not. For the engines that do not, there is a port in the side of the block that is used for this purpose. It is best to check with a knowledgeable heavy diesel mechanic, dealership service center or shop manual to determine which port is pressure and which is for filtered oil to return to the block and oil pan. Always check the ports with an oil pressure gage just to be 100% certain which is the pressure and which is return port. The hydraulic lines used for this type of installation do not need to be of large diameter. The typical size is 3/16 or ¼ inch inside diameter.
With both of the by-pass systems described above, the full flow filter is still retained and utilized. The full flow filter must be changed at the filter manufacturers recommendations. The by-pass filters are generally changed based on the results of oil analysis testing or at the by-pass filter manufacturer recommendations. Typical change intervals on by-pass filters are 25,000 miles/1-year for gasoline engine cars and light trucks.
Heavy diesel engine by-pass filters are changed in accordance with oil analysis test results or a specific hourly or mileage change interval that is determined by trend analysis (monitoring and testing of used oil over a period of time in order to establish change intervals based on the method in which the particular engine is operated), or the by-pass filter manufacturers recommendations.
Dual Remote oil filtration system
Another very popular type of by-pass system is called a Dual Remote oil filtration system and is the only one of its kind. It is manufactured and patented by AMSOIL INC. The method that this filtration system functions is as follows: a valve block machined to accept a full flow filter and a special by-pass filter is mounted remotely in the engine compartment or under the vehicle, typically on the frame. A special machined or cast aluminum adapter threads on the existing full flow filter location and two hydraulic lines are attached to it and routed to attach to the remote mounted valve block. The full flow filter functions exactly the same as if it were still mounted on the engine, but it is remote mounted and typically in a location where it is much easier to access. The valve block internal orifices and metering valves control the amount of oil that is routed through the by-pass filter, after passing through the full-flow filter.
Filtered oil is returned back to the engine adapter via a return hydraulic line exactly as it would be returned to the engine if the full-flow filter was still mounted on the engine. The hydraulic lines used for this type of system are typically 13/32 inch inside diameter because they also have to be large enough to allow for the full flow volume of oil to flow through them. Another benefit of by-pass systems is that oil capacity can be increased significantly, depending on the size of the filters selected.
There are numerous types of by-pass filters and systems on the market. Some examples are Frantz, Lubrifiner, Purifiner and AMSOIL. They vary in terms of cost, function and installation. They manufacture both single by-pass units and Dual Remote by-pass oil filtration units and are the most effective and easy to install systems and their cost is very reasonable when compared to other by-pass systems. They are also extremely easy to service and change filters by simply spinning off the old one and installing the new one.
The difference between the AMSOIL By-Pass Filters and others is the unique design of the filtering media and the patented construction of the filter element. The high capacity oil filtration medium is a special blend of virgin wood and cotton fibers, formed into discs, stacked, and compressed. The center tube is all steel, perforated for oil flow, and wrapped with a fine mesh cotton screen.
The by-pass filter will trap dirt particles to 3 microns with almost 100% efficiency and to 1 micron with about 85% efficiency and the medium’s fibers can remove up to a pint of water (something that no full-flow filter can do). Channeling is eliminated with the inclusion of a hydraulic follower plate activated by a sophisticated internal pressure system. The filter is enclosed in a strong steel canister and threads onto the valve block unit.
Note that the diameter of a human hair is approximately 90 microns. This helps to give you a perspective on just how small of particles the AMSOIL by-pass filter can remove. One micron equals 0.000039 inch or 0.001 mm.
Most people aren’t going to install a by-pass oil filtration system, so it's a good idea to purchase the best full-flow oil filter with the smallest micron filtering and the highest efficiency rating to ensure the highest possible
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