Caterpillar’s S∙O∙S Services Fluid Analysis and Interpretation

Cat S∙O∙S Services provide information to help you make maintenance decisions, reducing owning and operating costs, and maximize component life. This is a quick and easy program to help your equipment remain productive, and maximize the value of your investment. The two components of S∙O∙S Services are Oil Analysis and Coolant Analysis.

Oil Analysis

The S∙O∙S oil analysis tests have been developed by Caterpillar engineers and chemists. Tests such as Element Analysis, Oil Cleanliness Analysis, and Oil Condition Analysis are examples of the standard tests offered in the S∙O∙S program

Component Wear Rate

Component Wear Rate analysis evaluates the wear taking place inside the lubricated compartment. Your S∙O∙S Analyst uses the results of elemental analysis and particle count tests to evaluate the wear. Trend analysis and proprietary wear tables are then used to determine if wear rates are normal or abnormal. Listed below are some common areas of concern.

  Elevated Test Results Possible Sources
Diesel Engines Iron, chrome

Iron, chrome, aluminum

Lead, aluminum, iron

Sodium, potassium, copper

Silicon greater than aluminum, iron lead

Soot, iron, lead, chrome

Cylinder liners, piston rings

Cylinder liners, piston rings, aluminum piston skirt

Lower rod and main bearings, crankshaft

Coolant contamination

Dirt, cylinder liners, piston rings, bearing overlay

Soot wear on cylinder liners, piston rings, bearings

Powershift Transmissions Silicon, iron

Aluminum, copper, iron

Copper greater than lead or tin

Wet clutch friction material

Torque converter

Bronze bushing and thrust washer

Hydraulic & Steering Systems Iron, chrome

Silicon greater than aluminum, iron, chrome

Cylinder and rod wear

Dirt entry, pump wear, cylinder and rod wear

Differentials & Final Drives Silicon greater than aluminum, iron, chrome, nickel

Copper greater than lead or tin

Dirt entry, gear wear, bearing wear

Bronze bushing or thrust washer


Oil ConditionOil Condition analysis is used to determine if the oil has degraded. Tests are done to look at the viscosity, oxidation, sulfation and nitration of the oil. All lubricated systems risk oxidation damage of the oil. Therefore, it is recommended that oil samples from all compartments be analyzed for oil condition. Your S∙O∙S Analyst uses established guidelines or trend analysis to determine if the oil has reached then end of its useful life.

Oil Contamination

Oil contamination tests are performed to determine if anything harmful has entered the oil. This analysis relies on results from the following tests: elemental analysis, soot, particle count, fuel dilution, water, and coolant. The S∙O∙S Services program has guidelines for the level of contamination allowed in the various compartments of a Cat machine.

Coolant Analysis

Inadequate cooling system maintenance can eventually lead to system problems or even engine failure. S∙O∙S Services offer a two-level Coolant Program to determine if your coolant has the right chemical balance for maximum system protection and cooling efficiency.

Coolant Reporting

Diesel engines are designed to operate at higher temperatures and higher energy levels than in the past. Today’s heavy-duty diesels produce a tremendous amount of power from a small package. Cooling systems have to absorb more heat with smaller cooling systems and less coolant. A cooling system may also be transferring heat away from turbochargers, transmissions, hydraulic systems and other components. In addition, used coolant disposal requirements have become more stringent and expensive. You may be extending coolant drain intervals, recycling coolants or reconditioning coolants to reduce the disposal costs. For all these reasons, S∙O∙S coolant analysis is highly recommended to achieve optimum performance and the full life designed into today’s machines and engines. Four types of analysis are performed during coolant testing; Coolant Type, Boil and Freeze Protection, Coolant Condition, and Contamination.

For more information, see your Cat dealer today or visit

This article appeared in the june 2012 issues of the Associated Construction Publications (ACP) magazines national section.

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