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Technical
Service Bulletin 98-1
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Extended Oil Drain Intervals
Oil
service intervals are pre-determined by engine manufacturers (OEM's) and
are designed to provide maximum engine protection under a wide variety
of conditions. While a majority of equipment owners follow these guidelines
there is a growing trend to extend oil service intervals beyond the OEM
recommendations; However, Extended Oil Drain Intervals (EODI) are not
for everyone. To fully understand the risks involved you must look at
the key factors affecting EODI's.
Engine
lubricating oil is often referred to as the life blood of the engine.
This analogy is not made simply because the oil circulates through the
engine but more importantly because the oil performs critical functions
necessary to maintain engine performance and maximize useful service life.
There are two basic types of oil available today: Mineral and Synthetic
oils. While these oils are completely different in composition and beyond
the scope of this service bulletin, they must still meet the American
Petroleum Institutes (API) qualification criteria recommended by the engine
manufacturers. There are many suppliers of oil in the market today and
not all meet the stringent requirements of the API standard. Insuring
your oil meets these requirements and understanding the factors affecting
the engine oil is the first step before extending your oil service interval.
Equipment
operating extremes of Heat, Cold, Idle Time, Airborne Contaminants,
and Engine Load adversely affect engine oil. Excessive Heat will break
down engine oil and create deposits in the engine adversely affecting
engine life. Severe cold will limit the ability of the engine oil to lubricate
at start-up and may add unwanted moisture and unburned fuel to the oil.
Extended Idle Time can result in increased amounts of unburned fuel entering
the oil resulting in oil dilution and inadequate lubrication. Extreme
dust conditions may tax even the best air filtration system adding fine
contaminants to the oil overloading the additive package that keeps them
in suspension. Heavy loads on the engine can produce extra heat putting
a greater demand on the cooling system and increasing the importance of
cooling system maintenance during EODI's. Off-road operation will likely
see more of these extremes than on-highway operation.
Engine
designs today are cleaner burning with reduced emissions and make
excellent candidates for extended oil drain intervals; However, most customers
cannot afford to buy new equipment every year and normally fleets have
a mixture of equipment varying in vintage and service life. As piston
rings and valve guides wear in the engine, combustion by-products increase.
These combustion by-products end up accelerating oil additive depletion
and create harmful deposits on internal engine surfaces making the engine
less likely to benefit from an EODI.
Oil
filters remove contaminants from the oil before they generate wear
on engine component surfaces. There are many filtration products offered
in the industry today with some claiming to allow for extended oil drain
intervals. The fact is, the filter alone will not extend the life of engine
oil. The filter has one function, and that is to filter contaminants from
the oil. While most filters today do an excellent job in filtering, the
trend of extending oil drain intervals 2 to 3 times the normal service
interval has pushed the materials used in the manufacture of filters to
the limit. Adhesives, Rubber Compounds, Filter Media, and even the steel
construction in spin-on filters needs to be designed to meet the extended
period of time they are expected to be in service. Before considering
an EODI make sure the filter manufacturer will warranty their product
when used in this manner.
If
after considering all the factors affecting extended oil drain intervals
you feel your equipment is a candidate for EODI's you will need to develop
a test program to determine what length EODI is right for your equipment.
To determine the correct length EODI you must first implement an oil analysis
program to develop history on each piece of equipment scheduled for extended
oil service. This will allow you to determine if there is any usable life
left in the oil. The primary indicators will be Silicon (dirt), Viscosity
(Oil Film Strength), Soot (Combustion by-product), and Total Base Number
(TBN). Most engine manufacturers have oil analysis guidelines. Typically
you will want to keep your silicon within 15ppm of the initial oil sample,
your Viscosity within the original oil grade specifications, Soot below
3%, and the TBN number above 3. Each piece of equipment will vary and
the key is to look for trends in the analysis. If oil analysis indicates
you can extend your service interval you then need to move out in steps.
Oil analysis should continue at the normal service interval and in increments
of 20% thereafter until the analysis shows the useful life of the oil
deteriorating. Once the maximum limit on the oil is reached the change
interval should be set at the mileage of the previous sampling prior to
indications of oil deterioration. Example: Normal service interval = 16,000
miles (25,000 km). Oil analysis performed at 16,000 (25,000 km), 19,200
(30,000 km), 22,400 (35,000 km), 25,600 (40,000 km), and 28,800 (45,000
km). If oil analysis indicates problems at 28,800 (45,000 km) the change
interval should be backed off to 25,600 miles (40,000 km). This will allow
for variables in operation and environment.
Extended
oil drain intervals are not without risk and short term cost savings benefits
should be balanced equally with engine performance and reliability. With
all of the factors affecting the engine oil it is easy to see why OEM's
have traditionally been conservative in setting oil drain intervals. If
you think your equipment is a candidate for EODI program, do some research.
Check with your Filter, Engine, and Oil manufacturer for guidance. If
you're not doing oil analysis, start a program. Review your filtration
package and most of all understand the potential risks involved. If not
properly implemented EODI short term savings are offset by expensive repairs
and downtime further down the road. Always dispose of used engine oil
and filters properly.
For additional information, contact:
Filter Manufacturers
Council
P.O. Box 13966
Research Triangle Park, NC 27709-3966
Phone: 919/406-8817 Fax: 919/406-1306
www.filtercouncil.org
Administered by Motor & Equipment
Manufacturers Association
Created June 1998
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