Oil Filtration Fundamentals

Motor oil becomes unfit for service after a period of use for two main reasons. First, the accumulation of contaminants in the oil and secondly the chemical additives change; additive depletion and oxidation. These two factors cause deterioration of the oil and prevent it from doing its job of lubricating and cooling engine parts.

How Motor Oils Become Contaminated


Road Dust and Dirt

Design limitations of air cleaners, some oil fill caps, and crankcase ventilation systems allow some dust and dirt to enter the engine. Leaks in the intake system also permit unfiltered air to enter the engine. However, proper maintenance of the engine and its accessories can minimize the amount of contaminants entering the lubrication system and extend engine life.

Metal Particles

Normal wear of parts in an engine produces very small metal particles that are picked up and circulated by the oil. Particles of road dust and dirt increase the rate of wear and generate larger metal particles that in turn are quite abrasive that circulate through the engine with the oil. While oil filters help keep these particles at a minimum, they can’t remove them entirely or to a particulate size that does not cause wear to moving parts.

Hand Covered in Dirty Oil

Combustion By-Products


Combustion produces water vapour, or steam. When engine temperatures increase most of the water turns into vapour form and goes out through the exhaust. However, when engine temperatures are low, such as; at start-up, warm-up and short-trip operation in low ambient temperatures, the water vapour condenses (turns into a liquid) on cylinder walls collects in the crankcase oil. This contamination if not removed (periodic oil changes) leads to the formation of sludge, rust and corrosion.


The combustion process produces acidic gases which, like water vapour, condense on cylinder walls at cold engine temperatures and also find their way into the crankcase oil. These acids combine with water to cause rust and corrosion. When water condensation in a diesel engine combine with its acid by-products produce what is know as sulphuric acid.

Soot and Carbon

Incomplete combustion produces soot, carbon and other deposit-forming materials. An engine running too “rich,” or with too much fuel, increases the amount of contaminants. In gasoline engines, light-load and low-speed operations increase these combustion by-products more than high-load, high-speed operations. Diesel engines produce more of these by-products with low-speed, high-load operations.

Fuel Dilution

When an engine is started or running abnormally, some unburned fuel in liquid form is deposited on cylinder walls. That means raw fuel leaks past the rings into the crankcase, where it reduces the viscosity of the oil. Dilution lowers the film strength of the oil and increases oil consumption. Usually this is a minor problem when engine operation is at high-speed or high-temperatures, but it can be a problem in vehicles consistently used for short-trip driving, (a.k.a city driving).

While all of the processes by which motor oil is contaminated are not fully defined, the use of high-quality motor oils such as AMSOIL synthetic motor oils allows operators continued protection of their engines along with extended drain intervals, all while limiting the contaminants in the oil and prolonging engine life.

Engine Wear

Automotive experts agree dirt is the number-one cause of engine wear. Analysis by Federal Mogul Corporation reports that 43.4 % of all engine bearing distress is caused by dirt. Engine dirt particles are so small – mere dust specks – and an engine is a highly sophisticated piece of machinery, crafted from the most durable metal alloys yet these minute particles can easily destroy any high-tech engine.

The answer lies in the fact that dirt particles are extremely abrasive. They consist of razor-like flakes of road dust and airborne grit drawn into the engine through the intake manifold, as well as manufacturing scarf and wear-metal particles generated inside the engine. These particles are carried by the oil into the precision clearances between bearings and other moving parts. Once they work in between these parts, they grind and gouge surfaces, altering clearances and generating more abrasive debris. This wear cycle continues, making precision components sloppy and fatigued until they fail altogether.

Filtration is the key to preventing costly engine repairs caused by dirt. Filtration removes contaminants by trapping and holding them outside the system of oil circulation. In order for a filter to be truly effective, it must be able to capture contaminants of all types and sizes. AMSOIL has developed a complete line of sophisticated filtration products designed to offer the best protection available against virtually all harmful engine contaminants.

Oil Filtration

Full-flow oil 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 the engine. A full-flow filter must be able to remove and hold contaminants without obstructing oil flow to the engine. Most filters on the market compromise the filtration of finer particles by using a thin layer of porous filter paper. These filters have almost no extended cleaning ability since they have a low capacity for storing dirt. These “surface-type” paper filters quickly become restricted as debris builds up on the paper surface.

Oil System Diagram

When this happens, the filter by-pass valve opens and allows unfiltered oil into the engine. Some low cost oil filters can actually become damaged by water saturation and destabilize under oil pressure thus allowing unfiltered particulate to remain in the oil. By-pass valve failure also remains a well-known problem among low quality manufactures that can lead to complete flow restriction in colder temperatures staving the engine of its oils supply.

AMSOIL Ea Oil Filters are made with premium-grade full-synthetic media. The strictly controlled processing of this media ensures accurate filter construction, and is what allows Ea Oil Filters to deliver higher capacity and efficiency along with better durability. AMSOIL Ea Oil Filters have significantly lower restriction than conventional cellulose media filters. Their small synthetic nanofibers trap smaller particles and hold more contaminants, resulting in lower restriction. During the engine warm-up period, Ea Oil Filter allows the oil to flow through the filter at colder temperatures than a typical cellulose filter. Thus, the additional filtering time decreases engine wear.

By-Pass Oil Filtration

An average full-flow filter traps particles as small as 20 microns. The filter can’t remove finer particles because the oil must be filtered quickly while removing most of the particles in the oil yet not restrictive to the oil supply. By-pass oil filtration uses a secondary filter with the purpose of eliminating nearly all contaminants in engine oil and not starving the engine during this process.

AMSOIL Spin-On By-Pass Filter

By-pass filters have high capacities and eliminate much smaller particles than full-flow filters, including those in the 2 to 20 micron range such as soot and sludge. The AMSOIL By-Pass filters operate by filtering oil on a “partial-flow” basis. It draws approximately 10 percent of the oil pump’s capacity at any one time and traps the extremely small wear-causing contaminants that full-flow filters can’t remove.

By-Pass filters have a high pressure differential, causing the oil to flow through them very slowly and allowing for the removal of smaller contaminants. It is called by-pass filtration because the oil flows from the by-pass filter back to the sump and by-passes the engine. This continual process will eventually make all of the oil analytically clean, reducing long term wear and can extend drain intervals even in diesel engines, (the harshest environment for a motor oil).

AMSOIL Ea By-Pass Filters use a two-stage pleated and layered cellulose/full-synthetic media to provide an efficiency rating of 98.7 percent at two microns.

Reduces Oil Changes

By cleaning the oil so completely, the AMSOIL Ea By- Pass Filter not only prolongs engine life but also the life of the oil itself. With the AMSOIL Ea By-Pass Filter, oil changes can be extended well beyond normal, in many cases virtually indefinitely, depending upon the conditions and severity of use.

Dual Remote: Patented Protection

Available only from AMSOIL, the Dual Remote Oil Filtration System replaces conventional full flow filters, mounting in any convenient location in the engine, and gives full-flow and by-pass oil filtration protection. With Dual Remote, filter changes are quick, clean and easy. It also increases an engine’s oil capacity, helping oil work better, not harder.

By-Pass Oil Filtration

An average full-flow filter traps particles as small as 20 microns. The filter can’t remove finer particles because the oil must be filtered quickly while removing most of the particles in the oil yet not restrictive to the oil supply. By-pass oil filtration uses a secondary filter with the purpose of eliminating nearly all contaminants in engine oil and not starving the engine during this process.

Oil Analysis

By analyzing used engine oil, a qualified lab can determine the degree of protection the oil is delivering and make certain the oil has not been contaminated. Oil analysis also can detect impending engine failure.

The combination of a superior lubrication and reliable oil analysis provides not only peace of mind over extended drain intervals, but also lower maintenance cost, less down time and an over all decreased operational cost.

Oil Testing For Quality & Contaminants
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