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Introduction

Oil analysis is a series of laboratory tests used to evaluate the condition of lubricants and equipment components. By studying the results of the oil analysis tests, a determination of equipment/component condition can be made. Primarily, this is possible because of the cause-and-effect relationship of the condition of the lubricant to the condition of the component sampled. Many of these cause and effect situations are outlined in this manual.

Oil performs several vital functions with many of them being interrelated. The ability of the oil to perform as designed can be determined by oil analysis. The following is a list of some primary lubricant functions that can be evaluated:

The inspection or analysis of lubricating oil has been used to check and evaluate the internal condition of oil-lubricated equipment since the beginning of the industrial age. Early methods included smelling the oil to detect the sour odor of excess acidity, rubbing it between finger-tips to check lubricity, and observing its color and clarity for signs of contamination.

Today, oil analysis programs use modern technology and laboratory instruments to determine equipment condition and lubricant serviceability. Oil analysis uses state-of-the-art equipment and techniques to provide the user with invaluable information leading to greater equipment reliability.

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Viscosity

Viscosity is one of the most important properties of lubricating oil. Viscosity is a measurement of resistance to flow at a specific temperature in relation to time. The two most common temperatures for lubricating oil viscosity are 40°C and 100°C. Viscosity is normally evaluated with a kinematic method and reported in centistokes (cSt). In used oil analysis, the used oil’s viscosity is compared to that of the new oil to determine whether excessive thinning or thickening has occurred.Viscosity Index (VI) is the change in flow rate of a lubricant with respect to temperature. Oil with a high VI resists thinning at high temperatures. Use of high VI oil is recommended in engines and other systems that operate at elevated temperatures.

Cause

Effect

Solution

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Water/Coolant Contamination

The presence of water in engines indicates contamination from outside sources, from condensation of moisture in the atmosphere, or from internal coolant leaks. Water is typically evaporated by engines at normal operating temperatures. However, water may remain in the oil when engine temperatures are too low for evaporation to occur. Other types of equipment, when operated at sufficient temperatures, also tend to evaporate contaminating water.Oil analysis offers an effective method of recognizing water/coolant contamination before a major problem occurs. Infrared analysis is used to determine water content in used oil. Results are reported in percent volume. The Karl Fischer method is used to measure water in systems that are sensitive to low moisture content. Karl Fischer results are reported in parts per million (ppm).

Cause

• Low operating temperature
• Defective seals
• New oil contamination
• Coolant leak
• Improper storage
• Cracked cylinder head
• Weather/moisture
• Product of combustion
• Oil cooler leak

Effect

• Engine failure
• High viscosity
• Poor lubrication
• Corrosion
• Engine overheating
• Acid formation
• Reduced additive effectiveness

Solution

• Inspect for cracked cylinder head
• Inspect heat exchanger and oil coolers
• Evaluate operating conditions
• Evaluate equipment use vs. design
• Avoid intermittent use
• Check for external water/moisture sources
• Change oil filter

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Fuel Dilution

Fuel dilution of crankcase oil by unburned fuel reduces lubricant effectiveness. The thinning of the lubricant can lead to decreased lube film strength adding to the risk of abnormal wear. Depending on certain variables, when fuel dilution of crankcase oil exceeds 2.5% to 5%, corrective action should be taken. Fuel dilution is measured by gas chromatography. The results are reported in percent volume.

Cause

• Incorrect air/fuel ratio
• Extended idling
• Stop and go driving
• Defective injectors
• Incomplete combustion
• Incorrect timing

Effect

• Metal-to-metal contact
• Poor lubrication; oil thinning
• Increased overall wear
• Piston ring wear
• Decreased additive effectiveness
• Risk of fire or explosion
• Reduced fuel economy
• Decreased oil pressure
• Reduced engine performance
• High operating cost
• Shortened engine life

Solution

• Check fuel lines, leaking injectors or seals, pumps
• Analyze driving/operating conditions
• Check spark timing
• Avoid prolonged idling
• Change oil and filter more frequently
• Evaluate equipment and use vs. design
• Check fuel quality
• Repair/replace worn parts

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Solids

Solids represent a measurement of all solid and solid-like constituents in the lubricant. The makeup of solids depends on the system. In diesel engines, fuel soot is usually the major constituent measured. In non-diesel components, wear debris and oil oxidation products are measured. All solid material is measured and reported as a percentage of sample volume or weight.

Cause

• Extended oil drain interval
• Environmental debris
• Wear debris
• Oxidation byproducts
• Filter leaking or dirty
• Fuel soot

Effect

• Shorter engine life
• Filter plugging
• Poor lubrication
• Engine deposits
• Sludge formation
• Accelerated wear
• Decreased oil flow
• Lacquer buildup

Solution

• Drain oil, flush system
• Eliminate source of environmental debris
• Evaluate equipment use vs. design
• Evaluate operating conditions
• Reduce oil drain intervals
• Change filter

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Fuel Soot

Fuel soot is composed of carbon and is always found in diesel engine oil. Laboratory testing is used to determine the quantity of fuel soot in used oil samples. Stringent exhaust emission regulations have placed greater emphasis on fuel soot levels. One of the most significant impacts of reduced emissions is control of particulate emissions, which resulted in greater soot levels in the crankcase. The fuel soot level is a good indicator of engine combustion efficiency and should be monitored on a regular basis for possible maintenance action.

Cause

• Improper air/fuel ratio
• Improper injector spray pattern
• Poor quality fuel
• Incomplete combustion
• Clogged air induction
• Defective injectors
• Improper equipment operation
• Low compression
• Worn piston/rings

Effect

• Poor engine performance
• Harmful deposits or sludge
• Increased wear
• Shortened oil life
• Lacquer formation
• Clogged oil filters

Solution

• Ensure fuel injectors are working properly
• Change oil
• Evaluate oil drain intervals
• Check compression
• Avoid excessive idling
• Check fuel quality

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Oxidation

Lubricating oil in engines and other components combines with available oxygen under certain conditions to form harmful byproducts. Heat, pressure and catalyst materials accelerate the oxidation process. Byproducts of oxidation form lacquer deposits, corrode metal parts and thicken oil beyond its ability to lubricate. Most lubricants contain additives that inhibit or retard the oxidation process.Differential infrared analysis offers the only direct means of measuring the level of oxidation in oil. Note: A new oil reference is required for accurate measurement of oxidation. Results are reported on an absorbance scale.

Cause

• Overheating
• Extended oil drain interval
• Improper oil type/inhibitor additives
• Combustion byproducts/blow-by

Effect

• Shortened equipment life
• Lacquer deposits and engine sludge
• Oil filter plugging
• Increased oil viscosity
• Corrosion of metal parts
• Increased operating costs
• Increased overall wear
• Decreased engine performance

Solution

• Use oil with oxidation inhibitor additives
• Shorten oil drain intervals
• Check operating temperature
• Evaluate equipment use vs. design
• Evaluate operating conditions

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Nitration

Nitration products are formed during the fuel combustion process when combustion byproducts enter the engine oil during normal operation or as a result of abnormal blow-by past the compression rings. These products, which are more common in oils used to lubricate natural gas- and propane- fueled engines, are highly acidic and create deposits and accelerate oil oxidation. Infrared analysis represents the only method of accurately measuring nitration products in oil. Results are reported on an absorbance scale.

Cause

• Improper crankcase scavenge
• Low operating temperature
• Defective seals
• Improper air/fuel ratio
• Abnormal blow-by

Effect

• Nitrous oxides introduced into environment
• Acidic byproducts formed
• Increased cylinder and valve train wear
• Oil thickening
• Combustion chamber deposits
• Increased acid number

Solution

• Increase operating temperature
• Check crankcase venting hoses and valves
• Ensure proper air/fuel mixture
• Perform compression check or cylinder leak-down test

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Total Acid Number (TAN)

The total acid number is the quantity of acid or acid-like constituents in the lubricant. An increase in TAN from that of the new lubricant should be monitored. The TAN of a new oil is not necessarily zero since oil additives can be acidic in nature. Increases in TAN usually indicate lube oxidation or contamination with water or an acidic product. TAN is an indicator of oil serviceability.

Cause

• High-sulfur fuel
• Overheating
• Excessive blow-by
• Extended oil drain interval
• Improper oil type

Effect

• Corrosion of metallic components
• Promotes oxidation
• Oil degradation
• Oil thickening
• Additive depletion

Solution

• Shorter oil drain intervals
• Verify correct oil type in service
• Check for overheating
• Check fuel quality

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Total Base Number (TBN)

The total base number is an expression of the amount of alkaline additives in the lubricant that are capable of neutralizing the acid products of combustion.  A new oil starts with the highest TBN it will possess. During the time the lubricant is in service, the TBN decreases as the alkaline additives neutralize acids. TBN is an essential element in the establishment of oil drain intervals since it indicates whether the additives are still capable of providing sufficient engine protection.

Cause

• High-sulfur fuel
• Overheating
• Extended oil drain interval
• Improper oil type

Effect

• Increased acid number
• Oil degradation
• Increased wear
• Corrosion of metal parts
• Acid buildup in oil

Solution

• Use low-sulfur fuel
• Follow manufacturer’s recommendations for oil drain interval, and decrease if engine is operated under severe conditions
• Verify TBN of new product and use correct oil type
• Change oil or top off with fresh oil
• Test fuel quality

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Particle Count

Fluid cleanliness is critical in hydraulic and other systems where high fluid pressure and velocity are involved. Excessive fluid particulate contamination is a major cause of failure of hydraulic pumps, motors, valves, pressure regulators and fluid controls. Failure due to excessive particulate contamination is normally segregated into three areas:

• Performance degradation
• Intermittent failure
• Catastrophic failure

Particle count measurements allow the user to monitor hydraulic system contamination levels on a scheduled basis. Scheduled analysis of hydraulic fluid to include particle count is recommended by most equipment and hydraulic component manufacturers.

Cause

• Water contamination
• Machining burrs
• Filling techniques
• Oil oxidation
• Contaminated new oil
• Worn wiper seals
• System generated debris
• Built in contamination
• Defective breather

Effect

• Performance degradation
• Intermittent failure
• Wear
• Plugging
• Leakage
• Pressure overshoot
• Momentary hesitation
• System failure

Solution

• Filter new oil
• Change hydraulic fluid
• Inspect/replace filters
• Check particle sizes
• System flushing at high pressure
• Check air breather
• Evaluate equipment vs. design
• Evaluate operating conditions

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Wear Metal/Elemental Analysis

Elemental analysis is used to evaluate and quantify wear metal elements, additive elements and contamination elements. Wear metals are analyzed to pinpoint problem areas through trend analysis. By analyzing the additive elements, the oil type can be verified, e.g., hydraulic oil, transmission fluid or engine oil. Contamination elements are reviewed to determine lubricant serviceability and to pinpoint causes of problems indicated by other test results.

Following are the sources of the elements analyzed and their function in a component:

Wear Metals

Additive Elements

Contaminant Elements

Quality Equipment Oil Analysis Program

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Oil Sampling Methods

To properly evaluate machine conditions, the oil samples submitted for analysis must be representative of the system from which they are taken. For best results, follow these guidelines:

1. The machine being sampled should be brought to normal operating temperature. Oil should be recirculated, if appropriate. This will ensure that insoluable and semisoluable contaminants are uniformly dispersed throughout the system. Samples taken from machines that have been inactive for long periods are not representative.
2. Oil samples should always be taken in the same manner and from the same sampling point.
3. Do not sample a machine immediately after an oil change or after a large amount of makeup oil has been added.
4. Use a clean dry container to draw the oil sample. Ship samples in the plastic bottles provided in the package. Hydraulic fluids or other oils submitted for a particle count analysis should be submitted in the super clean bottles, which are provided when special testing is requested.

Sample Gun Method

The oil test package includes a plastic sampling bottle used for collecting and shipping samples. A special inexpensive sampling gun is also offered as an option, together with convenient lengths of plastic sampling tubing. The plastic sampling bottle fits directly into the sampling gun, and the oil sample can be drawn directly from the machine into the sampling bottle. The sampling gun allows the user to draw representative samples quickly and with a minimum of effort. Procedures are as follows:

1. Measure a sufficient length of plastic sampling tubing to reach from the sampling gun through the sample aperture and into the machine sump or reservoir. If the machine has a dipstick, the tubing should be measured against the dipstick to establish the proper sampling depth.
2. Loosen the nut on the sample gun head, insert the free end of the sampling tubing through the nut (about 1/2 inch past nut) and tighten the nut to compress the sealing ring to obtain a vacuum-tight seal. Screw a clean plastic sampling bottle into the gun adaptor.
3. Holding the sampling gun upright, draw oil into the bottle using the piston lever until oil is within 1/2 inch of the top. To stop the oil flow, break the vacuum by partially unscrewing the bottle. Remove the bottle from the adaptor, screw the cap on tightly and wipe the bottle clean. Fill out the unit or machine identification number on the bottle label.
4. Replace the plastic tubing after each sampling to avoid sample cross-contamination.

Sample Valve/Petcock Method

Care should be taken to install the valve on the lube system in a location that will ensure representative oil samples can be drawn. The exterior of the valve should be wiped clean prior to sampling to ensure that no external contamination finds its way into the oil. Stagnant oil should be drained from the valve by drawing a small oil sample into a waste oil container just prior to collecting the oil sample in the plastic sampling bottle. Screw the bottle cap on tightly and wipe the bottle clean. Fill out the unit or machine identification number on the bottle label.

Oil Drain Method

Clean the area around the drain plug thoroughly to avoid sample contamination. Allow some of the oil to drain into a waste oil container prior to collecting the oil sample. Place a clean dry sample bottle into the oil stream and fill it to within 1/2 inch of the top. Screw the cap on tightly and wipe the bottle clean. Fill out the unit or machine identification number on the label.

Note: When taking oil samples from hydraulic systems for particle count analysis, special care must be taken to ensure the samples are representative and that they are contamination free. Use the special super clean bottles to sample oils for particle count analysis.

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