An oily wise man once said, “There’s no such thing as engine oil that’s too clean.” This is probably true but needs to be viewed in context, which the OEMs do. In cost-effective fashion, engine manufacturers develop oil filtration systems “good enough” to meet the needs of the engine. The big questions are whether that can be improved upon and whether it’s worth your while to do so.
Oil in an engine crankcase gets contaminated with all sorts of junk, starting with the sand, dirt, and miscellaneous metal from manufacture. From there, metals come from normal wear and carbon, soot with diesels, combustion byproducts and oxidation byproducts are generated in normal use. If the air filtration system is damaged or ineffective, dirt can get past the rings to contaminate the oil. Dirt can also get in through a malfunctioning crankcase ventilation system. And if you thought the new oil you were pouring in is spotlessly clean, think again.
Hard contaminants (metal, silicon, carbon/soot) cause wear in and of themselves and also deplete the additive package of the oil as it deals with them. Combined with heat and moisture, metallic particles increase the rate at which the oil oxidizes. When oxidation reaches the point past where the additives can neutralize it, sludge begins to form.
The size of the contaminant particles plays a major role in wear. The exact size of the “universally harmful particle,” about 20-plus microns (see “Filtration 101” sidebar), is not in too much debate, but at the smaller end it might be more variable according to the engine and whom you ask. Better full-flow filters have absolute ratings nearing 20 microns, but many engineers still think the 10-15 micron particles do the sneakiest harm in the long run. Oil filter efficiency improves in service, so a 25 micron filter will be getting everything that size and bigger, and some percentage of the smaller, especially as the media begins to load up and the larger pores are closed.
One obvious cure for a high contaminant load is to change the lubricant, but there’s a hitch. Today’s oils are better than ever. A good percentage of the time, you’re draining otherwise perfectly good oil just to get rid of the contaminants. That’s hard on the wallet, the global resource bank, and the environment.
You can buy replacement filters that have higher efficiencies than OE filters. Any improvement is a good thing but you have to balance other factors like flow and contaminant holding capacity. The premium filter manufacturers seem to manage quite well with absolute ratings as tight as the 15-20 micron range, but it’s a lot more difficult to package anything more efficient into a full-flow package—and there we are still above that 10-15 micron range. To go farther, you need to step into bypass filtration.
What Is Bypass Filtration?
Bypass filtration comes in several forms but the common concept is that it takes a small amount of the total oil flow and filters it through a much finer filter media than the primary full-flow oil filter uses. In concert with the primary filter, this greatly reduces the contaminant load in the oil.
Bypass filtration is often touted as an engine life extender, but it’s more immediate benefit is as an oil life extender. By reducing the contaminant load, and keeping it low, the additive package of the oil lasts longer. You can then safely extend the oil change interval without a high contaminant buildup or depleting the oil’s additive package. How much farther can you go? That’s highly variable based on the engine, operational situation, oil and the bypass system used, but the two- and three-times interval is most often doable and even farther is very possible.
Going back to the engine life-extending aspects, the benefits of fine bypass oil filtration are very real, but you must also grasp the real world. If you were to compare two well-maintained engines that used the identical oil and lived the identical life, one without bypass filtration and one with, what you would see is that the life extension comes at the end of a long life, maybe an extra 100,000 miles or more. That’s a substantial benefit but the question to ask is whether you will own the truck long enough to realize that benefit and recoup the expense? The cost of a bypass system is most likely recouped via longer oil change intervals, with engine life the icing on the cake. People who keep their rigs for long periods, and run the wheels off of them, have the most to gain with a bypass system. These are reasons why bypass systems are seen more in commercial operations than with private owners.
In 2006, the U.S. Department of Energy ran extensive tests on bypass filtration systems on both gas and diesel engines in its fleet. It was determined the full payback on the very expensive systems came as low as 72,000 miles for diesel buses and as low as 66,000 miles on gas Chevy Tahoes, mainly from the increase in the oil change interval. The oil condition was tracked via analysis and changed when indicated. Though “nothing special” mineral fleet oil was used, the oil change interval was safely doubled or tripled.
We decided to test a how quickly, and to what level, a Racor ABS bypass system could clean the engine oil in a Ford F-150 with a 5.4L gas engine. Racor, a division of Parker Filtration, is a big player in the filtration world. ABS, is short for “Absolute” because of Racor’s new high-efficiency filter media. The company replaced its long-running LFS system (7 microns absolute) with the ABS system a couple of years ago. The new ABS filters come in an aluminum housing with a choice of three filter element ratings, 3, 5 and 10 microns absolute. The housings come in various capacities from a couple of quarts to several gallons and fit engines from our “small” 5.4L to the giants of industry. The housings have restriction built-in to regulate the flow and not bleed too much oil pressure. To clean up a dirty engine, or break in a new one, you might start with the 10 micron element and work your way down to the 3. Starting with a fine filter on a dirty engine could lead to rapid loading of the filter.
Racor offers specific installation kits to fit many engines, but these are biased towards the commercial side. Still, many popular light-truck diesels are covered and some gassers. Otherwise, installing a “generic” bypass system is fairly simple because you need only to tap the filter’s feed line into the engine lube system and the return can go to any low pressure area, such as the oil pan, valve cover, or even the filler cap. That’s not beyond most home wrenchers.
We installed the ABS with 5,221 miles on the oil. We collected a used oil sample prior to the install and had saved back a sample of the virgin oil. After the installation, we collected another sample following 418 further miles. Particle counts were done on all three samples and the results were startling. In that short distance, the addition of the bypass system brought the dirty oil from an ISO (International Standards Organization) cleanliness code (see nearby sidebar) of 24/22/12 to 20/19/16. Ironically, 20/19/16 was the ISO code of the new oil, so in 418 miles, the oil was brought back to the cleanliness state of new oil right from the bottle. Long term tests are ongoing to see how long this conventional oil will go in actual service within the operational environment of our F-150.
The bottom line is that bypass oil filtration is all it’s cracked up to be, but the return on the investment may be long or short depending on how many miles per year are driven. The choice to install a bypass should be based on how long you intend to keep the truck.
Bypass Filtration 101:Things You Need To Know
Absolute Micron Rating: The smallest particle of which a filter can catch nearly 100 percent of (typically above about 98.5 percent) on the first pass of the oil.
Beta Ratio: Beta ratios show the particle size and the efficiency at that size. Beta 4=200 (or B4=200 means a filter will catch 99.5 percent of all 4 micron particles. You may also see double numbers, such as 2/20=10/75. The 2/20 indicates 2 and 20 microns. The 10/75 indicates the percentages (90 and 98.6667 percent in this case, see chart below). The 2, 10, 20, 75, 100, 200, 1000 Beta values are the common percentages, but you can convert any Beta values by dividing the number of upstream particles by the downstream (i.e., 100,000 upstream and 1,963 downstream= Beta 50.5, or 98.037 %).
ISO Cleanliness Code: There are two codes; a two-digit (e.g. 18/14), and a three digit (e.g. 18/14/11). With the two-digit, the first number indicates the number of particles larger than 5 microns and those larger than 14 for the second. The three digit code shows the particles above 4, 6, and 14 microns in size. The actual number in the code (e.g. the “18”) is the range of counted particles, in this case indicating 1300-2500 particles (see chart at right). Dropping from 18 to 17 indicates a 50 percent drop to 640-1300 particles.
Micron: One-millionth of a millimeter. One-thousands of an inch is 25 microns. A red blood cell is 3-5 microns in size. A human hair is about 70-100 microns in diameter. If you have really good eyes, you can see something about 40 micron in size.
Nominal Micron Rating: This expresses the smallest size of particle captured in one pass of the oil thru the filter. If you see a filter advertised as a “25 micron” filter, it’s most likely the nominal rating. To make this a useful spec, you also need to know the efficiency at that rating, which is expressed as a percentage. If you saw two 10 micron nominal-rated filters, one 20 percent efficient and another 90 percent, the latter is the better of the two.
Bypass Filters— Gas vs. Diesel
Our tests were on a gasser, but what about diesels? Abrasive soot is the bane of all diesels, especially the modern EGR-equipped diesels. Soot typically starts off in sizes under a micron in size but soon clusters with its cousins. That’s called agglomeration (and now you know where the term “glom” came from). Oil additives called dispersants prevent this but get depleted in the process. If the filter catches these particles before they agglomerate, the oil can do its job longer. Agglomerated soot becomes the nastiest black sludge you’ve ever seen. Capturing as much soot as possible is why bypass systems make more economic sense in a diesel because they can substantially extend the oil change interval with no engine durability penalty. Many commercial diesels are already equipped with very fine bypass engine oil filters.
Oil: Motorcraft Super Duty 10W30 CJ4/SM
Test Equipment: SpectroLNS Q-200 Particle Counter
Particle Counts: Counts per 1ml.
ISO Code: 20/19/16
Particles over 4 microns- 6,858
Particles over 6 microns- 2,936
Particles over 14 microns- 477
Pre Install, Used Oil, 5,221 miles:
ISO Code: 24/22/16
Particles over 4 microns- 143,894
Particles over 6 microns- 27,961
Particles over 14 microns- 454
Post Install, Used Oil, 5,639 miles (418 since install):
ISO Code: 20/19/16
Particles over 4 microns- 7,472
Particles over 6 microns- 2,608
Particles over 14 microns- 419