In the "Modern Trucking Techniques" of Land Line Magazine published a great article on Bypass Filter technology. Here it is....
Grime busters
By Paul Abelson, senior technical editor
Truckers today enjoy more time between oil drain intervals thanks to advances in engine and oil technology.
But, all the technology in the world is no match for the gook and grime
that builds up over time, eventually killing the effectiveness of your
oil – if you leave it unchecked.
Oils and engines have
gotten so much better that some engine makers now recommend oil drain
intervals of 25,000 to 30,000 miles. It’s mind-boggling when you think
about it. Most older engines on the road have recommended intervals of
12,000 to 15,000. Yet, today’s engines must handle more soot and still
have intervals nearly twice as long.
Since oils are so much
better, you have to wonder what it takes to extend preventive
maintenance and drain intervals on older engines.
Today’s
oils have improved additive packages. The chemicals suspend more soot,
in finer sizes than ever before. If for no other reason, 10-year-old
and older engines can safely extend oil drain intervals, even if only
for another 3,000 to 6,000 miles.
Extending intervals
involves more than just waiting longer to change your oil. It requires
establishing an oil analysis program and possibly adding a bypass
filtration system.
Engine makers establish recommended
intervals to protect themselves from claims during the warranty period.
The intervals are generally based on moderately severe duty cycles.
Recommended intervals are conservative. If something does go wrong, the
first thing manufacturers check is the service record. If maintenance
has been skipped or extended without a basis for doing so, warranty
claims will be denied, at least initially.
Know your oil’s enemy
The first tool for extending your drain interval is oil analysis. This
is not only recommended by the Technology & Maintenance Council’s
Recommended Practice 334, but also in RP 318, which discusses oil
analysis and how to use it.
Oil analysis tells you the condition of your oil. It detects
contaminants, determines the overall condition of the lubricants and
gives you a peek at component wear within your engine.
Simply, oil analysis tells you all about your oil’s condition so you
can make the best decision on how long to go between oil drains – and
not void your engine’s warranty.
A few years ago, a friend
had an engine part fail after 400,000 miles. He had paid for a
500,000-mile warranty with his new truck. The truck had a bypass
filtration system that allowed him to change oil and filters at
60,000-mile intervals.
The engine maker claimed he voided
the warranty by going so long between oil changes. The OOIDA member
brought in his stack of oil analysis reports, done at 15,000-mile
intervals over the life of the truck. Each one indicated the oil was in
good condition and had ample life remaining. The engine maker covered
the repairs to the engine.
While oil analysis will give you
an enormous amount of information about your oil, when you’re
establishing extended drain intervals there are two key elements to
keep your eye on.
You should track the total acid number –
TAN for short – and the total base number – abbreviated TBN. The total
acid number is a measure of how much acid from combustion is in the
oil. The total base number indicates the “base” or alkaline strength of
the oil additive package that neutralizes acids. The total acid number
must never exceed the total base number.
Once you have two
oil analysis reports, you can start a graph of the progression of the
total acid number and the decline of the total base number. Use the
vertical axis for the TAN and TBN and the horizontal axis for the total
miles on the oil.
Unless something catastrophic happens
inside the engine, the progression is relatively steady. Continue to
chart the progress each time you get a new report. Project the lines,
and make plans to change oil before the two lines cross.
A helping hand
Any filtration removes some contaminants so they don’t circulate with
the oil. Inside the engine, contaminants grind surfaces where moving
parts are separated only by a thin film of oil.
All oil needs to be filtered, but if the filtration is too fine, flow
will be constricted. Primary oil filters, called full-flow because all
the oil flows through them, capture particles as small as 25 microns. A
micron is one-thousandth of a millimeter.
Soot is formed
during combustion. Particles start out in the sub-micron size range but
grow because they stick together, which is referred to as agglomeration.
The particles grow as large as or larger than clearances inside the
engine where they scrape the metal surfaces. Wear metals enter the oil
and flow through the engine. The soot and wear metals then increase the
abrasion until particles become large enough to be captured in the full
flow filter.
Bypass filters capture smaller particles, but
because of the restriction caused by fine filtering, only a little oil
can flow through those filters at a time. Oil is diverted from the main
flow of oil, filtered, and returned directly to the crankcase. It
“bypasses” the engine, hence the name.
Bypass systems use
very dense filters such as compressed fibrous material, tightly rolled
filter paper, cotton mill waste and a variety of others. Some even use
rolls of toilet paper or paper towels.
Depending on the
density, the system can remove anywhere from 8 to 10 micron particles
down to 1 or 2 microns. By removing soot, wear metal abrasion is
minimized. Soot also reacts with chemicals in the oil’s additive
package. Removing soot extends the life of the additives, helping to
extend drain intervals.
Bypass systems require more oil.
Adding a bypass system increases total oil by 20 to 40 percent. So, if
all else is equal, a 20 to 40 percent longer drain interval is safe.
Factor in the reduction in wear metal and the slower depletion of
additives, and intervals can be safely extended beyond 60,000 miles,
but only if confirmed by oil analysis.
Some makers of bypass
filters claim you never have to change oil again, but they require new
filter elements frequently. Over time, the oil that fills the new
elements replenishes the additive package. It’s usually the equivalent
of a complete oil change every 50,000 to 80,000 miles.
Oil
drains can be extended safely, but only with proper planning and
constant evaluation. Or, you can change oil according to conservative
original equipment manufacturer recommendations.
Either way, regular preventive maintenance will help your engine last a long time.
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