Fun With Oil Filters

Oil filters – not the most charismatic subject, but one which can effect you greatly if it fails to do it’s job. Unfortunately, such a failure can be catastrophic when it occurs. Fortunately, oil filter failure is rare. Typically, we don’t think twice about the little spin-on filter that gets spun off and thrown away by the technician at your local service station or quick-lube establishment. They just spin on a new filter, fill your car with oil, take your payment, and send you on your way. You drive the specified number of miles and repeat the process. Your oil and filter are working just fine, right? Well, not really. Even when working properly, a standard automotive oil filter does a mediocre job at best. And that’s the way it is supposed to work.

Confused yet? OK, there is an explanation for these seemingly contradictory statements.

So, what’s the story? The story is your vehicle’s engine requires a constant supply of oil to operate. Without it, catastrophic failure is eminent. But not only does your engine need oil, it needs oil of the proper grade, with the proper performance characteristics, and it has to be kept clean if you engine is to last for an acceptable length of time.

In the early days of the automobile, oil filters weren’t even used. Cars at that time didn’t go very far very fast. Oil was circulated through the engine by the rotating engine parts, which literally splashed through the oil in the crankcase, distributing the oil as they moved. The oil that didn’t leak out or burn away was changed every few hundred miles. Neither the engines nor the oil used in them were very sophisticated. Filtration wasn’t seen as a priority.

This began to change as engine demands increased. The advent of pressurized oiling systems manifested the need for oil filters. Initially, oil filters were no more than small screens installed on the oil pump pickups to catch large pieces of debris that would damage the oil pump if ingested. In the 1920’s, pressurized filtration was introduced. This placed a filter downstream of the oil pump, but before the other lubricated parts of the engine. These early filters were of primitive designs, and didn’t work terribly well. They were also the point of possible leaks, and many auto manufacturers didn’t install them on their vehicles until many years later. Some cars, such as the ubiquitous air-cooled VW Beetle never used an oil filter, and these cars were imported to the US until 1979. Other manufacturers installed bypass filters. These filters received oil from secondary oil ports on an engine, not the primary pressurized oil passages. This design would filter a percentage of the oil being used and helped reduce particle contamination, but the parts of the engine with the highest lubrication demands were still fed unfiltered oil directly from the pump.

As engine operating speeds and longevity demands increased, so did the need for more efficient oil filtration. By the 1960’s most cars were produced with full-flow oil filters. This design made sure that all oil coming from the oil pump was filtered before it reached critical engine parts.

While automotive oil filters and filtration has evolved a great deal over the years, current systems are still a compromise. Designers have to balance the need for flow capacity, filtration efficiency, maintenance intervals, and cost. As a result, most standard automotive oil filters are effective in capturing solid contaminants down to about 40 microns in size, or approximately .0016 inches. Smaller particles are much less likely to be contained by the oil filter. The problem is that while 40 microns can be considered quite fine, many critical clearances in an auto engine are smaller than this. Allowing these finer particles to pass through the filter and into the engine causes accelerated wear as these contaminants slowly sand away at moving parts. As far back s the mid 60’s testing demonstrated the need for filtering oil to the level of 5 microns, or about .000196 inches.

Using filters that capture smaller particles could solve this problem, but then another problems arise; specifically, flow restriction and service life. Filters that capture smaller particles typically reduce oil flow due to the filter’s finer cell structure. Also, because the filter is capturing more dirt, it will clog up faster. To maintain flow, capture finer contaminants, and provide an acceptable service life, the physical size of the filter must be increased or an auxiliary, or bypass filter must be used. This creates yet another problem: making the filter actually fit in the space available on a vehicle.

So, how do we create an oil filter that will pass a sufficient volume of oil, trap fine dirt, and be small enough to actually fit on the vehicle? Enter exotic filter media.

Most conventional oil filters use a pleated paper element as the actual means of filtration. Performance characteristics of a filter are largely determined by the size of the surface area and the thickness of the element. Through the use of more advanced synthetic media instead of paper, greater dirt containment can be achieved while still maintaining proper oil flow. But, as you may have guessed by now, there is still a trade-off: price. Oil filters using synthetic media are more expensive.

Given the amount of compromises required of them, modern automotive full-flow oil filters perform quite admirably. The bad news is even greater performance is needed if you wish to maximize the life of your engine. The good news is that as a vehicle owner, you have options available to you if you wish to improve the quality and performance of the filtration of your engine’s oil. On a per-unit basis, the difference in cost between a cheap filter and a premium quality filter is nominal, usually no more than a few dollars.

So why don’t auto manufacturers install premium filters as original equipment on new cars? Simply, because it would not improve their bottom line; in fact, it would probably hurt it. As an individual, you are not encumbered by the same cost, design, and production constraints that the manufacturers face.

With the use of top quality motor oil and oil filters, you can extend the life of your vehicle’s engine, and with judicious use of increased oil change intervals, you can actually save money in the process.

No comments:

Post a Comment