Oil Analysis History
The first use of used oil analysis dates back to the early
1940s by the railway companies in the Western United States. Prompted by the
purchase of a fleet of new locomotives, technicians used simple spectrographic
equipment and physical tests to monitor locomotive engines. As steam locomotives
gave yield to diesel locomotives, oil analysis practices by railways caught on.
By the 1980s oil analysis formed the basis of Condition Based Maintenance in
most railways in North America.
Owing to the success of oil analysis in the railways, the
American Navy used spectrometric techniques to monitor jet engines on their
aircraft in the mid 1950s. Around this time Rolls-Royce was also experimenting
with oil analysis for their jet turbines. Oil analysis began to spread and
programs were developed by the American Army and Air Force throughout the 1950s
and early 1960s. Then commercial oil analysis laboratories first appeared on the
scene in the early 1960s.
A detailed analysis of a sample of engine, transmission and hydraulic oils is
a valuable preventive maintenance tool . In many cases it enables identification
of potential problems before a major repair is necessary, has the potential to
reduce the frequencies of oil changes, and increases the resale value of used
What is Oil Analysis?
Oil analysis involves sampling and analyzing oil for various properties and
materials to monitor wear and contamination in an engine, transmission or
hydraulic system. Sampling and analyzing on a regular basis establishes a
baseline of normal wear and can help indicate when abnormal wear or
contamination is occurring.
Oil analysis works like this. Oil that has been inside any moving mechanical
apparatus for a period of time reflects the exact condition of that assembly.
Oil is in contact with engine or mechanical components as wear metallic trace
particles enter the oil. These particles are so small they remain in suspension.
Many products of the combustion process also will become trapped in the
circulating oil. The oil becomes a working history of the machine.
Particles caused by normal wear and operation will mix with the oil. Any
externally caused contamination also enters the oil. By identifying and
measuring these impurities, you get an indication of the rate of wear and of any
excessive contamination. An oil analysis also will suggest methods to reduce
accelerated wear and contamination.
The typical oil analysis tests for the presence of a number of different
materials to determine sources of wear, find dirt and other contamination, and
even check for the use of appropriate lubricants.
Oil analysis can detect:
Some wear is normal, but abnormal levels of a particular material can give an
early warning of impending problems and possibly prevent a major breakdown.
- Fuel dilution of lubrication oil
- Dirt contamination in the oil
- Antifreeze in the oil
- Excessive bearing wear
- Misapplication of lubricants
Early detection can:
Early detection with oil analysis can allow for corrective action such as
repairing an air intake leak before major damage occurs. Probably one of the
major advantages of an oil analysis program is being able to anticipate problems
and schedule repair work to avoid downtime during a critical time of use.
- Reduce repair bills
- Reduce catastrophic failures
- Increase machinery life
- Reduce non-scheduled downtime
One purpose of oil analysis is to provide a means of predicting possible
impending failure without dismantling the equipment. A person can "look
inside" an engine, transmission or hydraulic systems without taking it
Evaluating Used Equipment
A complete record of oil analysis may be a great tool for selling a used piece
of equipment. It shows the potential buyers how the equipment has been
maintained and how adjustments were made during its life. The history is a good
indicator of potential future repairs and overhaul requirements.
One potential use of oil analysis is in the evaluation of used equipment
being considered for purchase. Without knowing the amount of operation of the
oil being analyzed, this test should be considered conclusive only if it
indicates a problem. A good report could result from either no problems or a
short length of service of the oil.
Some of the physical properties tested for and usually included in analysis of
an oil sample are:
- Antifreeze forms a gummy substance that may reduce oil flow. It
leads to high oxidation, oil thickening, high acidity, and engine failure if
- Fuel dilution thins oil, lowers lubricating ability, and might drop
oil pressure. This usually causes higher wear.
- Oxidation measures gums, varnishes and oxidation products. High
oxidation from oil used too hot or too long can leave sludge and varnish
deposits and thicken the oil.
- Total base number generally indicates the acid-neutralizing
capacity still in the lubricant.
- Total solids include ash, carbon, lead salts from gasoline engines,
and oil oxidation.
- Viscosity is a measure of an oil's resistance to flow. Oil may thin
due to shear in multi-viscosity oils or by dilution with fuel. Oil may
thicken from oxidation when run too long or too hot. Oil also may thicken
from contamination by antifreeze, sugar and other materials
Some of the metals tested for and usually included in analysis of an oil sample
and their potential sources are:
- Aluminum (Al): Thrust washers, bearings and pistons are made of
this metal. High readings can be from piston skirt scuffing, excessive ring
groove wear, broken thrust washers, etc.
- Boron, Magnesium, Calcium, Barium, Phosphorous, and Zinc: These
metals are normally from the lubricating oil additive package. They involve
detergents, dispersants, extreme-pressure additives, etc.
- Chromium (CR): Normally associated with piston rings. High levels
can be caused by dirt coming through the air intake or broken rings.
- Copper (CU), Tin: These metals are normally from bearings or
bushings and valve guides. Oil coolers also can contribute to copper
readings along with some oil additives. In a new engine these results will
normally be high during break-in, but will decline in a few hundred hours.
- Iron (Fe): This can come from many places in the engine such as
liners, camshafts, crankshaft, valve train, timing gears, etc.
- Lead (Pb): Use of regular gasoline will cause very high test
results. Also associated with bearing wear, but fuel source (leaded
gasoline) and sampling contamination (use of galvanized containers for
sampling) are critical in interpreting this metal.
- Silicon (Si): High readings generally indicate dirt or fine sand
contamination from a leaking air intake system. This would act as an
abrasive, causing excessive wear. Silicon is also used as a anti-foam agent
in some oils. more
- Sodium (Na): High readings of this metal normally are associated
with a coolant leak, but can be from an oil additive package.
Taking an Oil Sample
It is important to get an oil sample that is representative of all of the oil in
the machine. Remember, your analysis will be based only on the sample that you
send in for analysis. Always have the oil hot and thoroughly mixed before
sampling. Handle hot drained oil with care — it could cause serious burns.
The easiest way to obtain a sample may be when the oil is being drained for
an oil change. Sampling at this time usually involves letting some of the oil
drain and then catching a sample in an appropriate container.
Samples also can be obtained without draining oil by suctioning out through
plastic tubing routed down into the oil reservoir.
In any case, it is important to have an appropriate container and follow
sampling directions thoroughly. Remember, many of the tests are for measuring
materials on a parts per million basis, so safe, effective sampling is needed.
Cost and Convenience
Cost of oil analysis will vary according to the laboratory and extent of the
analysis. Typical charges are $10 to $30 per analysis. The expense easily can be
justified if it alerts the owner of a major problem that can be corrected and
will help prevent downtime when the machine is needed.
Several companies have developed oil analysis kits that make oil analysis
convenient. These kits include the sample bottles, suction pump and tubing, and
possibly a pre-addressed, postage-paid mailing container.
The reasonable cost and convenience of oil analysis for use makes it
another management tool that should be considered by anyone wanting to do
preventive maintenance. .
Results of the laboratory analysis are typically returned in two to seven days
after the lab receives the sample. Results are returned to the owner for review.
The laboratory may note when the analysis shows an abnormal condition and issue
a caution or recommendation accordingly (Figure 1).
A typical analysis report is included in Table I. It shows how detection can
predict engine problems. Other typical recommendations might be:
- Example 1: Bearing metals indicate wear Inspect all bearing areas
for wear Resample at 1/2 interval
- Example 2: Unit is in satisfactory condition Resample at normal
- Example 3: Abrasion indicated Inspect air filtration system Upper
cylinder wear indicated Excessive fuel dilution Resample at 1/2 interval
Optimum Maintenance Interval
Most maintenance experts realize the oil change intervals for both engines and
transmissions are decided by the "average need." No two pieces of
equipment have the same preventive maintenance needs. Each machine has different
imperfections and is used under different conditions. Operators doing smaller or
lighter jobs can cause different conditions on engines and transmission wear
than those that occur during more extended use. When using oil analysis to
determine maintenance intervals, there is little guesswork. Records show that
some equipment can safely run two or three times longer than recommended
intervals. The oil analysis may show that you are changing the oil more often
than necessary — or not often enough.
By eliminating too frequent oil changes, you reduce the cost for oil and
servicing and also reduce the amount of used oil to deal with. This is an
important pollution prevention method — reducing the source!
Oil sample analysis saves you repair and maintenance dollars, has the
potential to reduce used oil and increases resale value of equipment.
These are average numbers used but depending on your type of equipment may be
higher or lower. Most reports have charts listed on the back to explain the
severity of that component in ppm.
|Table I. Engine problems predicted with oil analysis.
||What to Check
|Silicon (Si) and
|10 to 30 ppm
||Air intake system, oil filter plugging, oil filler cap and breather,
valve covers, oil supply
||100 to 200 ppm
||Wear of cylinder liner, valve and gear train, oil pump, rust in system
||Excessive oil consumption, abnormal engine noise,performance problems,
oil pressure, abnormal operating temperatures, stuck/broken piston rings
||10 to 30 ppm
||Piston ring wear
||Excessive oil blow-by and oil consumption, oil degradation
||10 to 50 ppm
||Bearings and bushings wear, oil cooler passivating,radiator corrosion
||Coolant in engine oil, abnormal noise when operating at near stall
||40 to 100 ppm
||Extended oil change intervals
|Copper (CU) and
|10 to 50 ppm
||Bearing lining wear
||Oil pressure, abnormal engine noise, dirt being ingested in air
intake, fuel dilution, extended oil drain intervals
||10 to 30 ppm
||Piston and piston thrust bearing wear
||Blow-by gases, oil consumption, power loss, abnormal engine noise
|2 to 5 ppm
10 to 30 ppm
|Wear of bearings
||Excessive oil consumption, abnormal engine noise, loss in oil pressure
|Lack of lubrication
||Fuel dilution, blow-by gases, oil oxidation, carburetor choke,
ignition timing, injectors, injector pump, oil pressure
|Coolant leak or condensation
||Coolant supply, gasket sealed, hose connection, oil filler cap and
|* Significant as wear metal, only for engines using
unleaded and diesel fuel.
Figure 1. Example of oil analysis report.
|OIL TEST RESULTS
|UNIT NO 99999: OIL USED:
EL CHEAPO SAE GRADE:20 COMPONENT:ENGINE COOLANT:GLYCOL
MAKE:TT MODEL:C-60 ENGINE MANUF:CHEVROLET HORSE POWER:427 FUEL
|RECOMMENDATIONS FOR LAST SAMPLE ANALYSIS
EXCESSIVE FUEL DILUTION
OIL IN SAE 10W GRADE RANGE
CHECK BLOW-BY (COMPRESSION)
RESAMPLE AT NORMAL INTERVAL
CHECK FUEL PUMP
|As a result of the excessive fuel dilution, the oil has
one SAE grade, and we are seeing upper cylinder wear.