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I am writing this column from my daughters home in southwest Washington State. It was not the original plan, but a volcano in Iceland prevented my flying to Europe on vacation. That was followed within a day or two by the premature birth of my third grandson. So here I am, not floating down the Mosel and Rhine rivers on my way to Amsterdam, but instead visiting this new guy and his mom.

However, this does present an interesting circumstance which leads to my subject for this month.

Back in 1980 another volcano, Mount St. Helens, which is about 60 miles from here, blew its stack, filling the air with over 500 million tons of fine ash and dust. For many days after the eruption, cities east of here were covered by clouds of this material, which deposited fine, soft and yet abrasive glass particulates on everything at depths of up to 6 inches. I was working for Pennzoil at the time, and sales of automotive filters in the area were astronomical. People were changing air filters every day and oil filters about once a week to try to keep the abrasive grit out of their car engines and intake systems. I later heard stories of folks on the southern side of the mountain who had to wrap wet towels around their air-filter housings (not to mention their faces) to keep their engines running long enough to get to safety.

Filters play a very important role in the proper and long-term operation of your vehicles engine. They keep air clean and remove harmful particles from your oil, ensuring that your engine lasts. But how do we know that the filter is adequate for its purpose? What are the parameters that define a filters performance and how are they measured?

Lets take a look at filters and get a clearer understanding of the whys and wherefores of this necessary but often overlooked part of automobile engines. The basic components of todays spin-on, full-flow oil filter vary little from manufacturer to manufacturer, once you look inside the familiar domed and fluted steel canister. (Those indentations are in place so installers can get a good grip with their hand or an oil wrench.)

Starting at the base, youll find a gasket or O-ring to provide a good seal against the engine mounting, and then a threaded mounting plate that screws to the engine and holds the contents inside. The filter medium inside – a pleated ruff of porous paper or synthetic fibers – is wound around a central core, and braced with upper and lower caps, so it doesnt collapse as the oil flows through. Finally, a flat or coiled spring provides tension to ensure the whole assembly fits tightly together despite engine vibration or changes in pressure. Some filters also have an anti-drainback valve, which keeps the oil from draining completely, so its always there on engine start-up.

With various refinements, this design has been the basic format of oil filters for a number of years. A filter mediums performance is based essentially on the amount of surface area, and that is dictated by the number of pleats or folds in the medium itself. The efficiency is also affected by the type of material the medium is made from and treatments to the material.

The shell, or can as it is commonly referred to, is a deep-drawn steel which is very thin but extremely strong. It can handle pressures much higher than those experienced in normal engine operation. Base plates and gaskets are tailored to fit each unique engine design, so inventories must be pretty deep at installers and auto parts suppliers.

The single overriding parameter for these products is cost. A filter will be changed more than three times per year per vehicle on average, and must do all of the tasks required at a cost to the consumer thats about the same as one quart of conventional motor oil. That makes it very difficult to improve or innovate because with material cost increases (such steel and plastic prices), the profit margins are razor-thin. Due to competitive pressures, for years the thrust of filter design seems to have been centered on cost reduction.

For a consumer, the question is, how can I tell which filter is best? Are there any standards for filter efficacy? Are these reported by the filter manufacturers?

First, there are tests for filter performance. SAE J806 measures single-pass filtration efficiency. ISO 4548-12 measures multipass filtration efficiency. The results are reported as percent of particulate contaminants removed at a given micron level. Several filter manufacturers reference test results but with varying particle size, so it is difficult to get an apples to apples comparison.

Without a summary of objective measurements to compare filters, the only other approach to select the filter is by brand name. For oil marketers, the ultimate goal is getting consumers to select their product based on its brand. Filters present a different problem. While there are a large number of brands in the marketplace, only a handful of manufacturers actually make them. This is a classic private-label market.

The major companies that manufacture engine oil filters are Wix Filtration (formerly owned by Dana Corp. but sold in 2004 to private equity group Affinia); the Fram division of Honeywell; Champion Labs, which is part of UCI; Purolator, jointly owned by Bosch and Mann+Hummel; and the Baldwin division of Clarcor. Virtually all of the engine oil filters sold as factory fill and in the automotive aftermarket are sourced from this group of five companies.

In addition, each company manufactures a range of products, distinguished by cost/performance parameters. To differentiate quality, these products primarily use filter medium composition and efficiency (micron size). Like engine oils, some are categorized now by miles between oil drains, such as Frams Tough Guard, which promises 7,500 miles between changes, and its Xtended Guard, which delivers 10,000 miles.

Commodity filters are still tied to a 3,000-mile life, but with engine oil drain intervals going up and the use of oil life monitors increasing, the push to promote longer-lived filters is sure to continue.

One additional oil filter product is designed for use on high-mileage engines(sound familiar?). It contains engine oil additive in the form of a gel impregnated on the filter medium, which claims to condition the oil and maintain its pH. Its a good idea, but I wonder how long the gel stays on the medium before it is extracted and added to the engine oil. I also wonder how it impacts the oils existing additive system. While it may not present a significant problem, there is always concern about mixing additive systems and potential interactions that might make the engine oil less effective.

Some interesting and somewhat sobering information comes from a paper presented at the SAE Congress in Detroit in April by Yiannis A. Levendis, Ph.D., of Northeastern University (Design and Testing of a Novel Environmentally-benign Automotive Oil Filter, SAE 2010-01-0272). Levendis points out that in the United States alone about 500 million engine oil filters are disposed of annually. Most of these have only been drained of as much oil as will easily come out, and each can contain up to one liter of used oil. If these used oil filters go into any sort of landfill, they pose a tremendous contamination hazard. Crushing the filter and pressing out as much oil as possible (as many quick lubes do) is one way to reduce the potential for contamination. However, it doesnt get all of the oil.

Levendis proposes that an oil filter could be made from a honeycombed ceramic, and his paper presents some interesting data on the efficiency of such a filter compared to a conventional filter. It offers an alternative to current practice that makes a lot of sense.

The one significant concern for a ceramic filter is the cost. Obviously, this filter will be more expensive. How much more is not clear from the paper and could undoubtedly be a real roadblock to general use. One thing that makes this an attractive choice is the fact that the spent ceramic filter can be crushed, the oil fully extracted, and the ceramic reused to make a new filter.

Environmental concerns also are behind cartridge-type filters, which require a permanent housing to be part of the engine. Some European engines have used these for years, and General Motors Ecotec engine for the 2011 Chevy Cruze is a good example of how the idea is going global. The housings cap screws off, and a compact, pleated filter simply drops in. When its time for a change, the entire cartridge lifts out for disposal or incineration. Since the housing remains in place for the life of the engine, this also saves the trouble of cutting apart a regular filters steel can, rubber seal and other parts for recycling.

One other issue for filters is the problem of multiple base-plate and thread sizes, which sometimes result in the wrong filter being installed and oil leaking out. In some cases, it can be a serious enough mismatch that the filter actually falls off the vehicle and all the oil is lost. Thats a guaranteed new engine!

Fortunately, auto manufacturers are discussing this very issue. There is work under way to standardize the base plate, gasket and thread setup which will obviously make life a lot easier. However, with vehicles now averaging 10.2 years in age, it will be a long time before a single base-plate design will cover the U.S. fleet.

So, there you have it. Filters are important to long engine life. They keep potentially damaging particles in check and, for some designs, actually supplement the oils additive components. They can be a problem when it comes to disposal, and they can be misapplied. There are new designs coming out which might significantly change the equation. Everything from ceramic filter media to a standardized connection is on the drawing board, but these changes are a long way down the road.

Now, if the volcanoes will behave themselves, I may yet be able to make it to my cruise on the rivers of Europe.

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