To Bypass or not to Bypass
Bypass oil filtration may help extend drain intervals and engine life.
Deborah Lockridge
Senior Editor
Bypass oil filtration is certainly nothing new. As a matter of fact, it was the first type of oil filtering system used on cars. But it's getting more attention these days as truck owners look for ways to lengthen oil drain intervals, cut oil purchase and disposal costs, and extend engine life.
The energy bill signed into law by President Bush last month directs the Energy Department and the Environmental Protection Agency to study the benefits of oil bypass filtration technology. A smaller study at the Department of Energy's Idaho National Laboratory has already avoided 80% of oil changes on 11 buses outfitted with bypass filters. Many in the industry predict bypass filtration will be applied more widely in future engines, prompted by the push to increase drain intervals and engine warranty life even as engines change to meet tighter emissions standards.
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1. What Is Bypass Filtration?
All engines filter oil through one or more full-flow filters. However, the full-flow filter only goes so far in cleaning the oil, designed to protect the engine from the disastrous consequences of relatively large particles of wear metals and other contaminants. Or, as James Roberts, Shell technical service specialist, puts it, "The primary filter's just designed to take out rocks and chunks."
You can't do superfine filtration in a full-flow filter because it would impede the flow of oil through the engine. That's where bypass filtration systems come in. These take 5% to 10% of the oil out of the stream before it goes into the engine and run it through one of several types of devices that offer superfine filtration. From the bypass filter, the oil goes back to the sump, or oil pan.
All the oil eventually makes its way through the bypass filter – typically every 20 to 30 minutes of engine operation, according to the Technology and Maintenance Council of the American Trucking Assns.
"It's like a dialysis system for the engine," explains Matt Luntz, vice president of engineering for Refined Global Solutions.
(Bypass filters are not to be confused with the bypass valve that's built into your full-flow filter. The bypass valve is there in case the full-flow filter gets seriously plugged, at which point the bypass valve kicks in. This keeps the oil flowing, but the oil doesn't get filtered.)
There are different types of bypass filtration systems. Some simply offer a finer version of traditional pleated filter media, such as the one that is standard on Volvo engines in addition to two full-flow filters, or one that Wix has offered for some time.
Others use "depth" type filtration. These are typically a very thick media. Some of the earliest bypass filters, like the Luber-finer 750 that pretty much pioneered bypass filtration back in the 1930s, used "media" such as wood chunks and loose paper.
Over the years, depth filtration has used many different types of media, including cotton fibers and even rolls of paper towels. Today's depth filters often use more high-tech media, often combined with other features to enhance performance.
Companies offering depth filtration include Luber-finer, Oil Purification Systems, Perfect Filtration Systems, PuraDyn, Racor, Refined Global Solutions and Wix. Depth filtration can be very good at taking out not only fine particles such as wear metal, but also organic matter, such as sludge.
Much recent interest has centered around another type of bypass filtration – centrifuges – which remove particles heavier than the oil by spinning the oil at very high speeds. Centrifuge filters have been around for quite a while. Mack has had a centrifuge bypass filter standard on its engines for 30 years. Spinner II, probably the best-known aftermarket system, has been on the market in one form or another since 1983, and maker T.F. Hudgins has been selling centrifuges for almost 30 years. Fleetguard's centrifuge is called the Centriguard. Centrifuge systems have become more popular in the last couple of years because they are more effective at removing soot from the oil than other types of filtration. Soot removal has been a concern with EGR engines designed to meet new emissions regulations.
Several systems also claim to remove water and other liquids, including devices offered by Refined Global Solutions, Perfect Filtration Systems, Oil Purification Systems, PuraDyn and Racor. At least one system, PuraDyn, says it can replenish the additives in the oil.
Bypass filters may be mounted directly on the engine as original equipment, or may be mounted apart from the engine and connected by oil hoses. Bypass filtration is standard on Cummins, Mack and Volvo engines and is available as an option on other engines, such as the Caterpillar C11 and C13. Fleetguard offers a combination full-flow/bypass filter that is used in place of the regular full-flow filter. Truck makers – including Peterbilt, Western Star and Sterling – offer installation of oil bypass systems at the factory. Some truck dealers sell and install bypass systems, as well.
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2. The Case For Bypass
Because bypass filtration systems keep the oil cleaner, benefits include less wear on the engine, longer engine life, and the potential for extended oil drain intervals.
"There's kind of a constellation of environmental and economic pressures that are coming together to really make this technology viable," says RGS' Luntz. "We're trying to reduce our dependence on foreign oil, and the waste oil that is dumped into the environment has caused EPA to start putting pressure on the industry."
The big attraction of bypass filtration for most fleets, however, is the potential to extend drain intervals, especially as longer drain intervals are challenged by new lower-emissions engines.
"Bypass oil filtration technology was originally introduced to the trucking industry and positioned mainly as a way for fleets to extend engine oil life and oil drain intervals," says Brent Birch, laboratory manager for Champion Laboratories, maker of the Luber-finer Zgard bypass filtration system. "However, oil filtration is now getting a fresh look as fleets search for ways to maintain current oil drain intervals and boost protection of engine components from the side effects of EGR emissions-reduction technology." Many bypass filters underwent redesigns, and some new ones were introduced, to better clean the oil in EGR engines.
Record prices for crude oil are another reason for increased interest in bypass filtration. "When you look at crude oil at $67 a barrel and climbing, you're going to see more and more people talking about methods to reduce that operating cost," says PuraDyn President Kevin Kroger. "We're seeing fleets getting a 50%, 60% increase on their lubricating oils. In the past, they've always felt that changing oil is cheap insurance, but now you're starting to see that mentality change."
Claims for extending drain intervals through bypass filtration vary widely, from adding 5,000 miles to doubling your drain interval to 100,000, 200,000 – even 600,000 miles.
"It really depends a lot on your driving conditions, the type of engine (some have higher soot levels than others), the type of oil you're using, the type of driver, how old the engine is, if the engine already required a lot of makeup oil," says Keith Nye, vice president of sales for Perfect Filtration Systems.
Whether you're looking to extend your drain intervals 5,000 miles or 50,000, "the cleaner the oil, the better," says Shell's Roberts. "If the oil's cleaner, it's going to last longer. And you're adding additional capacity to the crankcase, so those are the two big advantages."
With the extra lines and canister, the bypass filter increases the total capacity of your oil system, by as little as a quart or as much as four gallons. Two extra gallons added to the usual 10 gallons is a 20% increase. The more oil you have, the more contaminants the oil can hold just by pure volume.
"If you've got a cup full of dirt and you put it in a gallon of water, and you put the same cup of dirt in 5 gallons of water, the one will look really dirty, the other will look almost clear," says John Clevenger, director of global product management at Fleetguard. The same goes for oil. You can disperse the dirt or soot over a larger amount of oil and get longer drain intervals.
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3. Hype or Hosanna?
However, the benefits of bypass filtration are not so clear to everyone.
While Caterpillar offers bypass filters, either paper or centrifugal, as an option on two of its engines, it's because of customer demand, says Bob Keene, customer value manager for on-highway products. "I can't figure out what good a bypass filter does other than adding more oil to the engine," he says. "But our customers like them, so we do have it available as an option."
Some critics say you may be able to get many of the same benefits of bypass filtration for less by spec'ing a larger oil sump.
"Any add-on bypass system could provide some benefit by the addition of extra oil capacity," says Fleetguard in its publication, "Separating Fiction From Fact: Bypass Filtration Systems."
"This added capacity provides some extended oil life due to the fact there is more oil. If the unit requires this added capacity to be replaced at the time of bypass filter service, the system will benefit from the addition of new clean oil with fresh additives. These two positive effects are often the only true benefits an add-on bypass system provides."
Another thing critics take issue with, particularly oil makers, is the claim of some bypass filter proponents that "oil doesn't wear out, it just gets dirty."
"The oil does get dirty, but it does more than just get dirty," says West Alexander III, senior staff engineer, engine oil technology, at Chevron Products Co. and current chairman of the API Lubricants Committee. "The oil suspends soot, wear debris and dirt, which can be physically removed from the oil by the filtration system. But the oil and its additives are being decomposed by oxidation and nitration. Acids, fuel and coolant are also being dumped in the oil. The byproducts of chemical reactions and fluid contamination are not removed by the filtration system. As the additives in the oil are depleted, the oil loses its ability to control deposits, disperse soot, neutralize acids and control wear. You're going to have oil consumption, high wear, rings sticking, increased deposits, increased fuel consumption, loss of power -- all those things happen when the oil additives are depleted. That's why the oil has to be replaced."
While bypass filtration may help the additives last longer by taking out some of the contaminants that cause them to deplete, there's still a limit to what they can do.
Two key contaminants that appear to be controlled by additives more than filtration are soot and acids.
There's a wide variety of opinions as to how well bypass filtration systems do in removing soot from the oil. Soot particles are formed during the combustion process and can cause excessive wear.
If oil is doing its job properly, soot is dispersed in the oil as particles that are a fraction of a micron – about the size of a human virus. That's too small to damage the engine, but also much too small to be removed by even the most efficient filter. It's only when the soot particles start to agglomerate – stick together to form larger particles – that they can be filtered out. And if the particles are agglomerating, it probably means the oil additives are wearing out.
"If the oil's performing adequately, not much soot gets filtered," says Mark Betner, heavy duty lubricant manager for CITGO Petroleum. "But when the oil becomes exhausted, that's when you're asking your filter to really step up to the plate – but when you think about that, should you change the oil anyway?"
Centrifuge systems are generally believed to do a better job at removing soot, but it's still unclear just how well they do.
Donaldson, which does not offer a bypass system, says it has done a lot of testing on bypass filters, both depth and centrifuge types, and hasn't found them to be very effective in removing soot.
"I think all of them have some success at removing soot, but we haven't found any that remove enough soot to extend the drain intervals out to where it benefits the operator," says John Hacker, director of product development-liquid filtration at Donaldson.
According to Fleetguard, however, high-speed centrifugal separation is the only proven filtration method to remove soot at a rate that maintains soot content levels in oil.
"You may take out 5% or 10% of the soot particles in a single pass through a high-speed centrifuge, but you get so many passes over a period of time, you can take it out," says Clevenger. "We have a lot of data that shows, if you had 5% soot you can take it down 1.5 to 2 points, almost a 50% reduction."
Clevenger says while centrifugal systems can take out the tiny soot particles, depth medias typically catch only soot that is agglomerated. "It still can be somewhat effective at extending oil life, but not nearly as effective as if you can get the soot before agglomeration," he says.
Tom Bock, vice president of sales at Oil Purification Systems Inc., notes that although soot is supposed to be suspended in the oil, "a lot of it isn't. It coagulates together. You'll trap soot in a 1- to 3-micron bypass filter. When you take the filter off, you'll find soot collected in the bottom of the canister."
In fact, Jim Weaver, executive vice president at T.F. Hudgins, makers of Spinner II, has a used filter bowl on his credenza with at least an inch of black gunk that he says is primarily soot. "All you have to do is talk to somebody that uses our product and have them show you the dirty bowl," he says. "Do we remove all the soot? Absolutely not. But we remove enough of it to help reduce the wear in the engine and extend oil drain intervals."
Champion Laboratories says it worked with an outside firm to test its bypass system with a fleet using Mack EGR engines. Using the bypass systems, Birch reports, the fleet was able to double the number of hours until a 3% soot loading level was reached.
Another important contaminant is crankcase acids, which are formed during combustion and can lead to high levels of corrosion and wear. Oils contain detergents that help neutralize the acids, but no filter can remove acids from the oil.
Some bypass systems claim they help prevent the formation of acid by removing water from the oil, usually through some sort of chamber that uses heat to evaporate the liquid. When water is combined with the sulfur in the oil and put under heat and pressure, sulfuric acid is created. Less water, less acid. But skeptics say there's just not that much free water in the oil system, and that the oil gets hot enough on its own to boil away any small amounts that do occur through condensation. In addition, heat itself can degrade oil.
Perfect Filtration Systems says its system absorbs water, with a water absorbent chemical baked into its cellulose media. "Our belief is the oil's already hot enough," Nye says. "One of the major breakdowns of oil is through heat; we don't believe you need to heat the oil hotter than it already is."
CITGO's Betner also points out that the "strong acids" created by water combining with combustion byproducts are not the only types of acid that build up in the oil. "There's the impact of heat over time, which causes oxidation and other acids – they call them weak acids; the filter can't do anything about them."
That's one reason PuraDyn says its system is designed to replenish the oil's additive package. "It's a critical part of safely extending the oil drains," Kroger says.
But oil makers aren't wild about the idea.
"I just shake my head, because it's not that simple," says Chevron's Alexander. "When you put something else in the oil, you can throw the balance off. For instance, wear-control additives lay down a sacrificial film on the surface of, say, a valve train, so it wears off that film, not the metal. If you put something else in the oil that's a surfactant – say a deposit control additive at the wrong level – it will get to the surface of those parts before the anti-wear additive can lay down that sacrificial film, so you end up with increased wear.
"If you're putting in an aftermarket treatment, whether it's pouring it in the crankcase or if it's in a filter, we're no longer responsible for oil-related failures," Alexander says. "The oil we're liable for is the one we put in the can and market to you."
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4. Bypass and You
It's vital that you do your homework when considering bypass filtration for your trucks.
"Truck owners should keep in mind, whether OEM or aftermarket, that not all bypass systems are equal," says Roman Goluch, product manager at International Truck and Engine Corp. "There is a huge sea of marketing information touting the benefits of company 'A' versus their competition. Remember that most companies can give information that shows how their system improves oil quality and engine wear, but this is true of almost any of the available bypass systems. How much is a different question. The bottom line is, the owner needs to weigh the cost of these systems with the benefits of the system they can realize."
Costs for bypass filter systems vary. At the low end, you can get Fleetguard's combination filter, which simply replaces the full-flow filter, for $20 to $40 (but keep in mind, this is a cost you'll incur every filter change). At the high end there's the Perfect Filtration Systems model, which can run $900 installed. Most others seem to run in the $300 to $600 range.
Don't forget that even though the oil may not have to be drained, the filter still needs to be changed or cleaned at regular intervals. Most systems require replacement filter elements or rotors, which can cost from around $15 to $70. Some, such as the Spinner II, are cleanable and reusable, so you don't have the cost of the replacement filter or the used-filter disposal costs, but there's a little more hassle and technician time involved there.
"I have seen good results with people that have used [bypass filtration], and there are other situations where they've basically wasted their time – and money," says Shawn Ewing, technical coordinator for heavy duty lubricants at ConocoPhillips.
Paybacks can come in the form of savings on oil, labor and used-oil disposal costs when you extend your drain intervals; in longer engine life and fewer repairs; and in resale value. The area most people focus on is extended oil drain intervals.
If you are looking to extend service intervals, keep in mind that the addition of bypass filtration by itself will not necessarily do it.
"Service intervals are a function of many factors," notes Fleetguard, "including oil quality, engine duty cycle, fuel dilution, engine soot production, oil sump capacity, full-flow filter construction and capacity, and bypass filter construction and capacity. The decision to push oil and filtration service intervals past OEM recommendations should include the OEM, the oil supplier and the filtration supplier. Each company is affected by the interval extension and may have warranty concerns."
If used-oil analysis shows acid and soot buildup are your main problems, bypass filtration may not be as cost-effective as it would be if your main problem is particulate contaminants, such as might occur if your trucks work in a dirty, dusty environment.
"If the oil runs out of TBN or base reserve (the number that refers to the ability of the oil to neutralize acids), it needs to be changed regardless of the soot loading or other properties of the oil," says Gary Parsons, global OEM and industry liaison manager for Chevron Oronite Co. "If the fleet or owner-operator is changing their oil because their TBN number is depleted, putting a bypass filter in is not going to change that situation at all."
As you're doing your analysis, make sure you're comparing apples to apples when it comes to filter efficiency.
"The terminology 'down to 1 micron' is purely a marketing issue," says Chris Greeson, senior technical services manager at Wix Filters. "All they're referring to is, eventually it will catch that size particle – and a piece of toilet paper will eventually do that. What you really want to know is how efficient it is." Greeson recommends that bypass filters take out at least 95% of 10-micron particles – and if you can get tighter, so much the better. Look for documented SAE testing.
Also ask for field test data, including engine tear-down analysis of wear. A valid test program will include a "control" engine run with the current practices. Testimonials may seem impressive, but they're not scientific proof.
Another consideration, particularly for aftermarket systems, is how the filter system will work on your particular vehicle(s).
"Look at the availability for oil lines, how you tap into the oil system, how various systems would actually physically mount on the vehicle, how much extra weight it adds, and the ease of service," Greeson says.
Ed Saxman, product manager, powertrain, at Volvo Trucks North America, notes that because their bypass filter is standard and is engine mounted, it eliminates oil lines that could offer more potential for leaks or damage as on a bypass filter that's added separately.
Once you've narrowed down the choices based on your homework, you can use oil analysis to see how well a particular filter system will work in your operation. If you already use oil analysis properly, you'll have a baseline you can use to compare. Outfit one or a number of trucks in your fleet with the system you're considering and see how they perform compared to trucks without the bypass filtration.
In fact, if you are hoping to use bypass filtration to extend your drain intervals, oil analysis is a must – as it is anytime you want to extend drains. That's why another consideration in deciding on bypass filters is the state of your maintenance program. As with any time you want to extend service intervals, you need a well-run maintenance program to make sure nothing's slipping through the cracks, because you have less margin for error.
Puradyn's Kroger says he's seen problems with this, especially at smaller fleets. "Technicians will think, 'If I just change this filter I'm in good shape.' They forget about the oil sampling. And you also have to continue to maintain the rest of your equipment. Don't fall into the complacency of thinking that just because you put this system on, you reduce your responsibility for maintaining your equipment."
TMC recommends that you make sure the aftermarket filter manufacturer warranties its product against engine damage caused by the device, because failures caused by aftermarket products are not normally warranted by the engine manufacturers.
Filter makers say problems caused by bypass filters would be extremely unlikely, as long as they are installed properly, because even if the bypass filter is not working, you still have the full-flow filter designed into the engine.
"The most important thing is the oil and the filter are a team," says CITGO's Betner. "I don't endorse anyone who says my oil's so good you never have to change your filter, and I don't endorse anyone who says you can run the oil forever because my filter's so good."
Maintenance for Profit continued...
