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 equipment.

What is Oil Analysis?

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:

• Fuel dilution of lubrication oil
• Dirt contamination in the oil
• Antifreeze in the oil
• Excessive bearing wear
• Misapplication of lubricants

Early detection can:

• Reduce repair bills
• Reduce catastrophic failures
• Increase machinery life
• Reduce non-scheduled downtime

Looking Inside

Evaluating Used Equipment

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.

Physical Tests

• Antifreeze forms a gummy substance that may reduce oil flow. It leads to high oxidation, oil thickening, high acidity, and engine failure if not corrected.
• 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

Metal Tests

• 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 on silicon
• 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

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

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

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 interval
• Example 3: Abrasion indicated Inspect air filtration system Upper cylinder wear indicated Excessive fuel dilution Resample at 1/2 interval

Optimum Maintenance Interval

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.
Indicator	Acceptable Levels	Engine Problem	What to Check
Silicon (Si) and Aluminum (Al)	10 to 30 ppm	Dirt ingestion	Air intake system, oil filter plugging, oil filler cap and breather, valve covers, oil supply
Iron (Fe)	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
Chromium (CR)	10 to 30 ppm	Piston ring wear	Excessive oil blow-by and oil consumption, oil degradation
Copper (CU)	10 to 50 ppm	Bearings and bushings wear, oil cooler passivating,radiator corrosion	Coolant in engine oil, abnormal noise when operating at near stall speed
Lead (Pb)*	40 to 100 ppm	Bearing corrosion	Extended oil change intervals
Copper (CU) and Lead (Pb)*	10 to 50 ppm	Bearing lining wear	Oil pressure, abnormal engine noise, dirt being ingested in air intake, fuel dilution, extended oil drain intervals
Aluminum (Al)	10 to 30 ppm	Piston and piston thrust bearing wear	Blow-by gases, oil consumption, power loss, abnormal engine noise
Silver and Tin	2 to 5 ppm 10 to 30 ppm	Wear of bearings	Excessive oil consumption, abnormal engine noise, loss in oil pressure
Viscosity Change		Lack of lubrication	Fuel dilution, blow-by gases, oil oxidation, carburetor choke, ignition timing, injectors, injector pump, oil pressure
Water/Anti-freeze		Coolant leak or condensation	Coolant supply, gasket sealed, hose connection, oil filler cap and breather
* Significant as wear metal, only for engines using unleaded and diesel fuel.

Figure 1. Example of oil analysis report.

Home