Maintaining your Cat engines and machines is one of your top priorities.  A good place to start is with S·O·S Services-oil analysis and coolant analysis. They are the fastest, most accurate, most reliable ways to see what's going on inside your Cat engines and machines. They are important steps toward increased productivity, less serious repairs, less downtime, and lower operating costs.

S·O·S Services is one of the most useful and important maintenance support programs available.  Here's why:
  • Detects problems early, so they can be repaired before they become major failures.
  • Helps you schedule downtime to fit your workload.
  • Monitors positives as well as negatives, so you won't have to pay for repair components that are not worn out.
  • Allows you to monitor maintenance schedules to verify that routine maintenance has been performed.
  • Enables you to better manage budgets by predicting repairs, downtime and equipment life.
  • Helps you develop a complete service history for each machine.  This proves invaluable when evaluating performance and planning replacement purchases.
  • Documents service history for a higher price at trade-in or sale.
For maximum protection, you need S·O·S oil sampling for all major oil-lubricated systems ( engine, transmission, hydraulic systems and final drives ) and S·O·S coolant sampling for you cooling systems.  Click to learn How To Take A Good Sample.  By pinpointing trouble early, you can avoid shut-downs for unplanned repairs or CATastrophic failures.

S·O·S Oil Analysis

The S·O·S oil analysis tests have been caeloped by Caterpillar engineers and chemists to evaluate the condition of your engines and machines, rather than the condition of the oil alone.  Following is a brief description of the standard tests offered in the S·O·S program.  Additional tests, such as viscosity, BN and AN, may be performed, if needed.

Wear Rate Analysis monitors wear by detecting, identifying and assessing the amount and type of wear elements in the oil.  The rate at which wear metal particles increase from sample to sample is as important as the quantity of the particles in the oil.  For this reason, regular sampling at specific intervals is necessary to establish wear rate trends for each oil-lubriCATed compartment.  The presence of other elements such as Silicon ( dirt ), Sodium ( salt water or coolant ), Potassium ( coolant ) are also monitored with Wear Rate Analysis.

Every oil-washed system - engines, hydraulics, transmissions and final drives produces wear metals in everyday operation.  If wear accelerates, the concentration of wear particles increases, signaling a problem.  Wear Rate Analysis allows you to find problems before they result in major repairs or machine failure.

Wear Rate Analysis

Wear Rate Analysis can detect particles that range up to about 10 microns in size.  Wear metal concentrations are expressed in parts per-million (or ppm).  The S·O·S Services program tests for the following substances: copper, iron, chromium, lead, tin, aluminum, molybdenum, silicon, sodium, potassium and zinc.

Two identical machines under identical conditions may generate wear particles at different rates.  Our S·O·S interpreters have access to a large database of samples for comparison with samples from you equipment.  However, your own machines provide the best guidelines for appropriate levels of wear metals in each compartment.  That's why trending is an essential part of Wear Rate Analysis.  After three samples have been taken from a particular compartment, a trend for each wear metal is established.  Our interpreters then compare subsequent samples to this trend line to quickly spot caiations as well as monitor gradual changes in concentration levels.  This attention to trend also assists with life cycle analysis, helping you optimize productivity.

When S·O·S oil analysis identifies an increase in the concentration of one or more metals, it can point to the wearing component most likely causing the increase and, often, the probable cause.  For example, a sudden increase in iron and copper in a hydraulic oil sample would probably indicate a problem with the hydraulic pump caused by either oil degradation or contaminant such as dirt (see chart, below)

Combinations of Classic Wear Elements
Engines–Top End
Primary Element
Secondary Element
Potential Wear
Probable Problem Area/Causes
Silicon (dirt)
Iron, Chrome, Aluminum
Liners, Rings, Pistons
Air Induction System/Filter Dirt Contamination
Chrome, Aluminum
Liners, Rings, Pistons
Abnormal Operating Temps., Oil Degradation, Fuel and/or Coolant Contamination, Stuck/Broken Rings
Molybdenum, Aluminum
Rings, Pistons
Blowby, Oil Consumption, Oil Degradation
Liners, Gears, Valve Train, Crankshaft
Abnormal Operating Temps., Lack of Lubrication, Contamination, Storage (Rust)
Engines–Bottom End
Silicon (Dirt)
Lead, Aluminum
Dirt Contamination
Lack of Lubrication, Coolant Contamination, Fuel Contamination
Silicon (Dirt)
Molybdenum, Aluminum
Cylinders, Rods
Dirt Contamination
Hydraulic Pumps
Oil Degradation, Contamination
Iron, Copper
Torque Converter
Bearing wear/failure allowing contact
Aluminum, Chrome
Roller or needle bearings
Bearing fatigue or failure
Final Drives
Silicon (Dirt)
Iron, Aluminum
Dirt Contamination, Clay Soils Contamination
Sodium, Chrome
Gears, Bearings
Water Entry, Preload Loss

Oil Condition Analysis

Oil Condition Analysis determines loss of the oil's lubricating properties.  An infrared analysis instrument is used to compare the properties of new oil to the properties of your used oil sample. This test allows our technicians to determine the extent to which the oil has deteriorated during use and to verify that the oil is performing up to specification during the entire oil change period. Oil Condition Analysis is similar to Wear Rate Analysis with one important exception: It evaluates chemical compounds in the oil rather than wear element particles.

Oil Condition Analysis detects soot, oxidation, nitration products and sulfur products/acids.  This test can also detect contamination by water, fuel and glycol from coolant.  If detected, specific contaminant tests are used to confirm readings.  Oil Condition Analysis focuses on:


Soot is found only in engine oil.  It is the insoluble residue of partially burned fuel.  It is held in suspension by the oil additive package and causes engine oil to turn black.  When soot drops out of suspension in the oil, it contributes to additive depletion and eventually increases oil viscosity.  Heavy concentrations of soot can cause bearing damage by starving contact surfaces of lubrication.


Oxidation occurs in engine, transmission and hydraulic oil when oxygen molecules chemically join with oil molecules.  This chemical reaction is accelerated by high oil temperatures, glycol contamination from engine coolant, the presence of copper, and from extended oil change intervals.  Oxidation causes the oil to thicken, form acids, and lose lubrication qualities, which threatens the life of your components.  Oxidized oil will cause deposits on engine pistons and valves, stuck rings, and bore polishing.  In hydraulic systems and transmissions, it can cause valve scuffing and sticking.

Nitration Products

Nitration occurs in all engine oils, but is generally only a problem in natural gas engines.  Nitrogen compounds from the combustion process thicken the oil and reduce lubricating ability.  If nitration continues unchecked, it can result in filter plugging, heavy piston deposits, lacquering of valves and pistons, and eventual failure.

Sulfur Products/Acids

Sulfur is present in all fuels and effects all engines.  During the combustion, fuel sulfur oxidizes, then combines with water to form acid.  Acid corrodes all engine parts, but is most dangerous to valves and valve guides, piston rings and liners.

Oil degradation may be the result of a number of factors and conditions, including extended oil change intervals, abnormal temperatures, or contamination by fuel, water or coolant.  Lower quality oils will degrade more rapidly than a premium quality lubricant.

Oil Cleanliness Analysis

Oil Cleanliness Analysis uses a Particle Count test for non-engine oil.  It detects both metallic and non-metallic debris (such as friction disc material) generated by wear, as well as dirt from outside sources.  This information, along with Wear Rate Analysis, permits a comprehensive evaluation of your hydraulic and power train systems.  This combination can detect potential failures not identified by Wear Rate Analysis alone.

Counting the tiny particles in an oil sample identifies harmful contaminants that shorten component life.  It can also pinpoint larger particles that signal imminent equipment failure.  Our SOS Services program finds these particles through a combination of tests that includes Particle Count.

Even particles far too small to see can cause damage.  In fact, oil that looks clean may contain particles that cause abrasive wear.  Particle Contamination:
  • Accelerates component wear
  • Reduces system efficiency
  • Diminishes equipment performance
The International Standards Organization (ISO) has developed a code system for convenience in discussing the cleanliness level of a fluid.  The system reports on particles at two important size Categories (>5 micron and >15 micron).  You may wish to learn more about this system of reporting oil cleanliness to better manage the life of your hydraulic and transmission components.  If you are interested ask us for form No. PEJT5025 Reporting Particle Count by ISO Code.

Particle Count, which is used for transmission and hydraulic system oil samples, is one of the two tests in the SOS Services program that look at particles.  The other is Wear Rate Analysis, which uses spectrometry to identify metal particles from 8 to 10 microns in size.  Unlike Wear Rate Analysis, Particle Count detects metallic and non-metallic particles from 2 to 100 microns.  However, Particle Count only reports the size and number of particles, not their composition.

Particle Count is the most efficient way to identify non-metallic particles in oil.  These may include silicon from dirt or synthetic friction material that signal deterioration in transmissions, steering clutches and brakes.  Gasket, seal, filter and hose material can also be detected.

Another benefit of Particle Count is its ability to detect particles larger than 10 microns that cannot be seen by Wear Rate Analysis or any other oil analysis test.  These larger particles are a sign of imminent failure if the problem is not corrected.

Particle Count is only used for non-engine oil samples because engine oil contains soot that cannot be distinguished from metal particles or debris.

Microscope Analysis

Microscope Analysis is used when an elevated particle count indicates contaminated oil.  The sample is filtered through a 5 micron patch and examined to determine source of the contamination.  A picture is taken and is included with the report.  Examples of this include:

Detection of Fuel, Water and Glycol.

The presence of Fuel, Water and Glycol are indications of problems which require immediate correction.  Fuel dilution reduces the oil's viscosity and destroys its lubricating properties.  Some unburned fuel may enter the crankcase past the piston rings, particularly if the engine is run at low idle for extended periods at cold weather.  Fuel dilution beyond 4% by volume, however can lead to piston ring sticking and failure of the engine bearings.  Glycol (coolant) contamination causes rapid oxidation of the oil and will lead to a major engine failure if not promptly resolved.  Water can contaminate an oil system by leaking in from the outside or condensing within a hot oil compartment or engine crankcase.  Water will cause the oil to form a sludge which can plug filters.  Oil contaminated with water passing between close fitting moving parts will cause "hot spots" leading to reduced component life or rapid failure.

S·O·S Coolant Analysis

Coolant or cooling system problems contribute to more than 50% of all engine failures.  These failures can be due to inadequate cooling system maintenance, incorrect concentration,  poor operational procedures such as extensive lugging or inadequate cool down procedures, or system problems such as stray electrical current or block heater failure.  These problems will eventually affect oil condition, and may cause oil oxidation or antiwear additive dropout.  Cooling system problems will also reduce the life of transmission and hydraulic components served by coolant heat exchangers.  S·O·S coolant analysis is a two-level program that does more than just check the condition of your coolant.  It determines the overall condition of the cooling system and can identify problems with maintenance procedures and operational practices.

Level 1:  Basic Coolant Maintenance Check consists of four analytical tests and four observational parameters that not only show major problems with the coolant, but can also predict some major cooling system problems.  Level 1 results can also determine when a Level 2 analysis is needed.

Level 2: Comprehensive Cooling System Analysis involves an extensive chemical evaluation of the coolant and its overall effects on the inside of your cooling system.  This series of comprehensive tests can identify subtle cooling system problems. Determine probable causes, and help prioritize the urgency of needed corrections.

S·O·S Services Online

Using our on-line program is a fast and easy way to monitor the effectiveness of your equipment maintenance program with no software required.  You're notified by e-mail when new oil samples are posted.  With S·O·S Services Online, you can view sample information, perform searches, and access online help.
Other screens allow you to view detailed descriptions of your oil samples, search for samples by several criteria, and review sample histories.  Though S·O·S Online minimizes paper filing and storage, you still have the ability to create and print graphs and reports.
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