If oil filters are an engine's first line of defense, why do you give them so little thought?
Chris Greeson is certain there is only one appropriate headline for an article about oil filters: “Dear Bubba,” he says, accenting his southern drawl. “Please remember the purpose of a filter. Physically, it’s only so big. It will only hold so much stuff.”
The senior technical services manager for Dana Corporation’s Wix brand knows that filters get little respect, despite the fact that they form the first line of defense between car engines and the microscopic particles that can tear bearings to bits. Consumers leave filters in place long after the cellulose is plugged. Mechanics grab the closest cans that will screw in place.
“It’s a commodity market. Two for five bucks and away you go,” he says of the stance taken by many shops.
Yet not all filters are created equal. Cheaper prices can equate to thin housings that are easily cracked; models that can’t withstand a heavy static burst accompanied by such things as thick oils at cold temperatures; or inferior gaskets that deteriorate and bleed lubricant. And don’t forget the effectiveness of the filter media packed inside the can.
The true difference is at the heart of the filter, explains Craig Read, regional manager for Honeywell Consumer Products, which markets FRAM designs. “All the money in filtration is in the media. I mean you’ve got to have the can, you’ve got to have a tapping plate, you got to have a gasket, it has to withstand 125 psi of oil pressure. So there’s not much you can do to scrimp there. Where you can save is in the media.”
Cellulose may be the base material used to filter oil, but filter makers closely guard their formulas for success. Wix premium filters, for example, incorporate a proprietary blend of cellulose, fiberglass and other manmade fibers, with a result that’s 25 per cent thicker than the media found in the company’s basic line, Greeson says. The difference between the premium and value lines equates to about four grams of captured dirt. But he won’t say any more about the blend.
The real test is how well the filters screen particles measuring between 10 to 20 microns in size, because these are the most damaging, Read says. “Above 20 microns, it can’t pass through the bearing surfaces, and below 10 microns it goes through the bearing surfaces without causing any scuffing.”
With measurements like these, don’t expect to be able to judge the quality of filter media with your naked eye. “To put that in perspective, a micron is 39-millionth of an inch,” he adds. “We’re talking about when you cut yourself last time, could you see the white corpuscles and the red corpuscles in your blood? That’s the size of the particles.”
It’s one of the reasons that Read warns against the Grey Market filters that he has seen becoming more dominant in the past year. They aren’t all they appear to be. “Some of those we tested, they visibly appear when you pick them up to be Sherman tanks. But when we tested them … they’re low on the efficiency side, and they’re about half the capacity.”
White Box alternatives, meanwhile, may include a shorter line-up of filters than their name-brand counterparts, adds Ramon Nunez, vice-president of filter product management for ArvinMeritor, which markets Purolator designs. “Most private label programs will only carry an oil filter line, an air filter line, and possibly a fuel filter line.”
The name-brand filters are usually the ones accompanied by marketing materials that can help close a sale, he says. “When you look at low-end products … typically what you see is a much more no-frills kind of a program, where most of them don’t even have catalogues.”
There can also be differences in the filters themselves. A silicone seal that may be attached to a name brand filter, for example, can last longer than its value-priced rubber counterpart. And while both seals might last between recommended oil drain intervals, it’s no secret that many customers appear willing to push the limits between visits.
It’s a matter of reading supporting documents. Wix, NAPA and Carquest filters, for example, are identical, right down to the last three digits in the part numbers, Greeson says.
Installation procedures for oil filters are deceptively simple, yet a surprising number of mechanics leave puddles of dark goo under cars.
“That’s why it’s extremely important that installers follow the filter manufacturer’s recommendations as far as tightening the filter when they go to change it,” Greeson says. “Three quarters of a turn (after the gasket contacts a sealing surface) on the large Ford spin, the static burst is about 275 lb., and that’s where the gasket pooches out.”
An overtightened filter can also lead to fatigue fractures that can be the source of leaks.
“Some people, they buy this nice wrench to take the filter off. They then use that filter wrench to put it back on and they dent the side of the can,” Greeson says. If you think a little dent isn’t much of a problem, consider that oil filters are pressure vessels — something that was easier to understand when the first Wix spin-on filter was released for Fords in 1955. The concave bottom looked like an aerosol can.
“Oil does not come into this filter like water running down a river. It comes in at high-speed pulsations off the gears of the oil pump,” Greeson explains. “You take a dent in the side of the filter can, or the dome of the can, and it will cause that area to flex back and forth. Pretty soon, you’ll fatigue fracture it.”
Then again, spinning a filter in place without a wrench is sometimes easier said than done when an engineer has decided to mount the filter beyond the reach of a technician with stubby fingers. (Consider a Pontiac Grand-Am that requires you to reach blindly behind the engine.) And with the installations on heavy-duty trucks, you’re likely going to need a wrench to tighten the filter in place. Just run your hand over the surface to ensure that you didn’t cause any damage in the process.
But loose installations can be just as troublesome.
“When you’re down in the pit and a guy wants to get the car out in 2-1/2 minutes, and they’ve got a greasy hand and a greasy oil filter in their hand, sometimes they don’t seem to get the right hand torque on it,” Nunez says. “But it feels good and they let it out.”
“We now ask for a turn and a quarter, and that’s so we hope we get the three quarters of a turn we really wanted in the first place,” Read admits. And FRAM has gone so far as to introduce a rubberized “SureGRIP” finish on filter cans to ensure a tight grip.
The days of spin-on cans, though, are numbered, as an increasing number of automakers such as Saab, BMW and Volkswagen introduce cartridge-based designs. North American manufacturers are already beginning to use them as well, bowing to the environmental concerns associated with piles of spin-on housings.
“Some of them are actually giving them a larger filter than they had,” Greeson adds, referring to an additional benefit of the evolution.
And the associated filter changes are a simple process. The cartridges are mounted high on the engines, and have dump valves on the bottom of the housings that can allow the lubricant to drain back into the oil pan as the filter is being changed. Simply unscrew the lid and replace the filter. But be sure to check the condition of the gasket or O-rings that seal the cartridge, and be careful not to crack the lid when replacing the top.
Regardless of the design, consumers may also be leaving their filters in place for longer than they should, with promises of extended oil drain intervals in their owner’s manuals.
If only they read the fine print.
“Extended drains, some vehicles have had a recommendation of greater than 3,000 miles (5,000 km) for 10, 15 years,” Nunez admits. “It has been in the last two to three that it’s making a definite presence.”
But such intervals are linked only to vehicles that don’t run under “severe service” conditions — an unavoidable reality for Canadian cars.
“There’s nobody in Canada that isn’t ‘severe service,'” Read
says. But he admits that extended drains are possible if you’re willing to conduct a regular oil analysis to set a vehicle’s maintenance schedule. Since he can access oil tests, he found that he could push his ’97 Grand Prix 13,000 km before needing to switch the synthetic oil.
Granted, most consumers aren’t interested in conducting an oil analysis program. It simply wouldn’t pay.
Oil filters can also face additional pressures during a Canadian winter, says Read.
“Everybody understands what happens when an engine doesn’t have enough oil pressure. You cook the motor. But you can have too much oil pressure, and typically we’ll see that in cold weather situations. Especially with people who like to drag the car along by the fan in the morning when the engine’s cold, or they don’t service their oil as frequently as they should so it tends to get thick and dirty.”
Greeson agrees. “Hopefully, there’s not 30- or 40-weight in the car because you’re going to have a hard time starting it anyway. But even with multi-viscosity oils, the 5W-30s that are so popular, the 5W-20s and the 10W-30s that have been popular for a long time, that oil is very thick and viscous, and it’s very hard for the oil pump to move it,” he says. “You could spike from 80 to 150, 160 (psi of oil pressure) very easily.”
The result should open a pressure regulating valve as long as it’s working as it should, but that depends on the age of the engine, the state of oil pump gears, and the wear on the valve itself because of the build-up of sludge that occurs over time.
“You can permanently deform the end of the filter and pooch the gasket out from a pressure spike, simply by getting up in the morning, going out, turning it on and revving it up a little bit,” Greeson says.
“I’ve seen it balloon a filter, I’ve seen it literally blow a filter right of the motor,” Read adds. “An oil pump is a straight hydraulic pump. When that valve sticks, the pressure goes up in relation to the rpm, and that what controls the oil pressure in an engine. This valve just bypasses and bleeds off excess flow, and if it sticks closed, kaboom!”
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