No One Rates Oil Filters, but Somebody Should

Question: A Toyota dealer advised me that upon changing my engine oil after the first 3,000 miles, I should use only a Toyota oil filter. The Toyota filter costs about $7.50. Such name-brand filters as Frahm and Purolator are sold from time to time at cut-rate stores for only $2.50. Is there any reason for sticking with the manufacturer's filter? J.B.

Answer: An oil filter can be as important as the oil, yet it is far more difficult to obtain information about the quality of the filter.

You can't determine the quality of an oil filter by looking at one. No independent organization rates or tests oil filters, as is the case with oil. And the price of an oil filter does not indicate its ability to protect an engine.

Auto manufacturers such as Toyota have a vested interest in recommending that consumers buy their more expensive filters. Virtually any part from a dealer will be more expensive than one from a discount retailer or auto parts store.

Most auto experts suggest that motorists can depend on major name-brand oil filters. Buying store brands, such as filters from Sears or K mart, involves more unknowns. If a filter carries no brand name and is not sold by a major retailer, you may have nobody standing behind the product.

Most of the major U.S. oil filter producers also sell to auto makers. Frahm, for example, makes filters for Honda as well as for retailers who apply their private label.

The filters sold under the name brand and private label, even though they are made at the same factory, may not be of equal quality. For example, filters Frahm sells under its own name are designed to catch 90% of dirt particles between 10 and 20 microns on the first pass through the filter, according to Gordon Jones, an engineer for Allied-Signal, which makes Frahm filters. (A micron is one-millionth of a meter.)

Dirt particles between 10 and 20 microns are considered the most harmful, because they are small enough to move through small passages in the lubricating system and large enough to cause abrasion in moving engine parts, Jones said.

But Frahm also makes filters under private labels that will capture only 80% of those dirt particles. Those filters contain less expensive filter elements, which are made of pleated paper that contains a secret mixture of glass, synthetic and cellulous fibers. Even so, Frahm believes its private-label filters are better than many competitors filters, which may capture as little as 60% of dirt particles on the first pass, Jones said.

The amount of dirt a filter can hold before it stops doing its job mostly depends on the size of the filter.

Many auto manufacturers in recent years have reduced the size of filters to conserve engine space and increase the interval between recommended oil changes. It has been a bad policy.

When an oil filter absorbs all the dirt it can hold, a safety valve opens to allow oil to circulate without any filtering. There is no way of knowing when that happens, though.

If you have a very small oil filter, especially the tiny three-inch filters that have become common, it is another reason to change your oil and filter more frequently than recommended.

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