The Engine Oil Filter

Oil filter is usually located on the bottom side of the engine as shown below.

Engine oil filter 1 picture #1

(Where the oil filter is located: Honda iTEC engine, sourced from Wikipedia)

Oil filters have a very important function and if your oil filter has poor quality, it can shorten the life of your engine and cause other parts to fail as well.  This small part of your car’s lubrication system plays an important role in protecting your engine from premature wear.  All the moving parts in the engine need clean oil to properly lubricate them.  We all know that as oil passes through the engine, it lubricates such parts as the valves, cylinder walls and pistons, camshafts and connecting rod and crankshaft bearings. As the oil flows over these various parts, it picks up small metal particles, dirt and other types of harmful grit. A good motor oil chemically holds these harmful deposits until it reaches the filter, where the deposits are trapped and removed from the circulating motor oil.

Engine oil filter 1 picture #2

Engine oil filter 1 picture #3

(The oil filters of the Mercedes Benz and Citroen)

Even though the oil pump pickup tube has a screen that removes large particles, the oil filter is still responsible for most of the filtering. Filter media is designed to trap the most harmful particles–those between 10 and 20 microns–the first time they reach the filter.

Engine oil filter 1 picture #4

(Oil Filter)


It is very important to choose a high quality oil filter because the internal construction and quality of the filter has a huge effect on the life of your car’s engine. One of the standards used to determine the quality of an oil filter is called filtration efficiency or particle size retention.  Particle size retention is the measure of how well a filter can retain particles of various sizes.

Another standard that a quality filter must meet is dirt-holding capacity.  This is the amount of contaminants that can be removed and held by the filter until the filter no longer works.

Hopefully these facts help you understand why a car oil filter is important.  A quality oil filter and quality motor oil work together to help our cars run more efficiently.



How often the oil filter should be changed?

Along with regular oil changes it is necessary for the extended life of your engine to change your oil filter on a regular basis also.  The ideal rule of thumb is to change your oil filter at every oil change.  To help lower the cost of vehicle maintenance and ownership many car manufactures say the oil filter only needs to be changed at every other oil change.  Most experienced mechanics will tell you the doing so can actually end up costing you more money in the long run.  Oil filters are relatively inexpensive and the benefits of a clean oil filter are many.

Most engines today have oil filters that have been downsized to save space, cost and weight.  The smaller filter has less overall filtering capacity and while it may be fine for a 5,000 km oil change interval the capacity may run out before a second oil change at 10,000 km.  Even with a larger oil filter, changing it every 5,000 to 8,000 km (depending on if you use synthetic oil) is highly recommended.

Engine oil filter 1 picture #5

(To keep track on the oil and oil filter change cycle is utmost important)

The oil filter helps prevent against abrasion and premature engine wear.  The filter’s main job is to remove dirt, debris, carbon, metal and by-products of combustion from the oil before they can cause damage to the engine.  Over time the oil becomes thicker and more polluted with these contaminants.  When the oil is changed and the old oil filter is left in, about several hundred mil-liters of the dirty oil remains in the filter, which then ends up with contaminating the new oil.

Today’s engines have what is called “full-flow filtration”.  The oil is picked up by the oil pump and sent through the filter before it’s circulated through the crankshaft bearings, cam bearings and valve train.  This is an efficient way of removing contaminants and making sure your engine is supplied with only filtered oil.  Over time, accumulated contaminants trapped in the filter begin to obstruct the oil flow; this can lead to lowered oil pressure and in some cases, overflow the dirty oil into the crankcase and engine, increasing engine wear.

Oil filters are relatively inexpensive and the benefits of keeping as clean oil filter in your car are many.  You will have a cleaner, cooler, well-lubricated engine, which in turn will give you optimized engine performance and better gas mileage.  Your vehicle will also emit less exhaust, reducing engine by-product emissions and your engine will last longer too.