Oxidation Loss of additive effectiveness Dispersancy, Corrosion, Wear Permanent viscosity drop in multi - grade oils

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1 Used oil analysis is comparable to a medical analysis with a blood test. Like blood, lubricating oil contains a good deal of information about the envelope in which it circulates. Wear of metallic parts, for example, produces a lot of minute particles, which are carried by the lubricant. These small metal particles can give information about the machine elements that are wearing, and can be detected by various methods Why test Lubricants. To check lubricant condition To check equipment condition Right oil is being used Efficient & effective maintenance practices Factors affecting oil life Degradation: Degradation refers to changes which happen to oil itself. Oils undergo destructive changes in property when subjected to oxygen, combustion gasses and high temperatures. Viscosity change, as well as additive depletion and oxidation occur to degrade the oil. Additive Depletion: Oil additives also have a limited lifetime. Some are consumed as oil ages. For example, alkaline additives get used up by neutralizing corrosive acids produced by the combustion process. When the oils reserve alkalinity (TBN) falls below the minimum safe level, higher component wear can be expected. Rust and corrosion inhibitors, anti-oxdidants and film strength agents also reach a point when they can no longer carry on. Additive "dispersants" suspend contaminants, deposits and other combustion insoluables until they are removed from the system by oil and filter change out. Once a dispersant becomes "loaded" any added sludge, resin or soot will cause the oil to dump whatever it has collected... and refuse to collect anymore. This results in a rapid build-up of engine deposits Main factors leading to oil degradation can be categorized as under: Oxidation Loss of additive effectiveness Dispersancy, Corrosion, Wear Permanent viscosity drop in multi - grade oils Contamination: Contaminants means something has gone into oil, which we don t want there. The causes of oil contamination are many, and can be classified according to source. Thus there is contamination coming from outside the system - dust (silica); liquids (mixture with other oils, water, other contaminated oil). The lubricant itself can produce or contain contaminants - wear, sludge (deterioration of the oil), soot, acids (oxidation of the oil, sulphur from fuel), temperature changes or extremes, fuel, anti-freeze, deterioration of packings and seals (e.g. deteriorating through the action of synthetic oils or brake fluids). Valvoline Technical Services Page 1

2 The other source of contamination is the wear of metal parts. Wear means the loss of solid material due to the effects of friction of contacting surfaces. Common contaminants and their source can be: Fuel combustion products Liquid fuel Solid particles (dirt, wear metals, etc.) Water Coolant additives Parameters and tests. 1. Tests for Oil Degradation a. Oxidation - All engines, transmissions and drive-axle component oils oxidize. A chemical reaction between oil molecules and oxygen takes place at high operating temperatures. This reaction increases viscosity, causes formation of insoluable engine deposits and corrosive acids which further increases component wear. While FTIR (Fourier Transform Infrared) gives exact measurement of Oxidation (measured as Absorbance / cm). Odour, Viscosity and Blotter spot test can also indicate possible Oxidation. b. Loss of Additive Effectiveness While Inductively Coupled Plasma (ICP) measures the exact additive elements in a given sample of oil, Following are also indicative of Additive effectiveness- Blotter Spot Insoluble Total Base No. (TBN) Infrared Analysis Valvoline Technical Services Page 2

3 Blotter Spot Test c. Viscosity Viscosity (Engine oils) - In the early days of the IC engine there were only monograde oils (e.g., SAE 20, SAE 30, SAE 50). By putting an additive into these oils, called a VI improver, multi-grade oils were created. The VI (viscosity index) improver is a flexible molecule, shrinks at low temperature and stretched out like a string at high temperatures. This allows the oil to remain viscous at high temperatures. Valvoline Technical Services Page 3

4 The viscosity of used engine oil is mostly measured at 100 C, and can drop for reasons of fuel dilution, and/or shearing of the VI improver. Viscosity can increase as a result of heavy contamination of the oil by soots, and/or oxidation of the oil. Viscosity (Industrial oils)- The viscosity of industrial oils, by contrast, is mostly measured at 40 C. The viscosity can be decreased by adding a less viscous oil, or by shearing of the VIimprover. The viscosity can be increased by adding a more viscous oil, and by oil oxidation (e.g. as a result of overheating). Following are the tests performed to check the viscosity C 40 C Viscosity Index d. Total Base Number (TBN) The alkalinity of an oil is measured by titration through an acid, and expressed in mg KOH/g. The comparison between the TBN volume of the fresh oil and that of the used oil allows the determination to be made of whether the used oil is still capable of neutralizing acid residues. These acids are produced by combustion (sulphur in fuel) and oxidation of the oil and oil additives. When the oil is in service too long, the TBN will drop significantly. Too low a TBN volume can be due to: heavy oxidation of the oil, when the oil has been in service for too long, of the oil level was insufficient, or due to a defective cooling system, producing overheating; use of a fuel containing a high sulphur content; use of an inappropriate lubricant; or contamination of the oil by fuel or water e. Total Acid Number (TAN) The acidity of the oil is measured by titration through a base, and expressed in mg KOH/g. 2. Tests for Oil Contamination a. Solid (Wear Metals & Dirt) Solid contaminants are either the dirt (Silica) or the metal particles that are result of wear of metal parts. The type of wear metal or dirt and its level in the given oil sample can be checked by Inductively couple Plasma (ICP) and the metal content is reported in ppm (parts per million) b. Water - The water-content in the oil is usually measured by the Karl Fisher apparatus. The possible causes of water introduction include (a) condensation, due to too low a working temperature, defective crankcase ventilation, stop and go in-service usage, and obstruction of the exhaust system;, Coolant ingress due to leakage at the cylinder head gasket, or damage of the engine block. Coolant water contains most often an anti-freeze based on glycol. Therefore a glycol test should be performed when water infiltration is suspected. The inhibitor in the anti-freeze agent is usually a sodium borate type. Following can also give an indication of possible water contamination Valvoline Technical Services Page 4

5 Appearance Crackle Test Infrared Analysis c. Fuel Dilution- Fuel Dilution of a use engine oil can be measured precisely by gas chromatography (GC) or by Fourier Transform Infrared spectroscopy (FTIR). However, reduction in Flash point also is an indicative of Fuel Dilution. It is evident that heavy Fuel dilution, oil is unfavourable for the engine, since it involves a lower viscosity and reduces the resistance of the oil film. The principal causes of dilution are a defective fuel injection system, a defective air inlet (obstructed air filter), incomplete combustion due to too low a working temperature, and badly regulated valves, or insufficient compression Wear Metals and Sources Contaminant Metals Valvoline Technical Services Page 5

6 Additive Elements Valvoline Technical Services Page 6

7 Physico-Chemical Tests on Used Oils Selection of the tests mainly depends on the purpose of testing and type of Oil Most common tests conducted are: 1. Appearance 2. Color 3. Odor 4. Kinematic Viscosity at 40 & 100º C. 5. Total Acid Number (TAN) 6. Total Base Number (TBN) 7. Flash Point 8. Water content 9. Insolubles in Pentane and Tolune 10. Foaming Advance testing would include tests like 1. Metal Analysis 2. Infrared Spectroscopy 3. Particle Count For Different types of oil, Oil companies and OEM recommend certain warning and rejection limits for used oil; the same are used to conclude the analysis. The field is advised to check the following whenever handling any complaint 1. Hazy Appearance 2. Changed in color (e.g. Red to Pink) 3. Emulsion in oil 4. Free water at the bottom of container A quick field test for analyzing the condition of diesel engine oil is the Blotter Spot test. In this test, a drop of oil is placed on the filter paper and allowed it to dry and settle for minimum 1- hour. The spot developed is then observed and condition of oil can be judged by observing the spread of the spot. Valvoline Technical Services Page 7

8 Oil Sampling Ask yourself few questions, before you decide for a sample analysis 1. Is the sample for Pro-active or reactive action? 2. If reactive. Have we got all the relevant information exact problem, history, symptoms of failures / complaint? 3. Do you really want the sample to be tested? 4. Are the symptoms, information shared gives you some clue what you need to get tested in the sample? 5. Is the sample collected representation of actual oil condition? 6. Is all the information submitted along with sample? Sampling Check Points 1. Take sample while engine is hot and oil well circulated 2. Use a new and clean sample bottle which should be rinsed preferably with oil being sampled 3. Draw sample from a petcock, installed in - line before the oil filter or from the oil pan or barrel (as case may be) using heat resistant tube and syringe. Only as a last resort take the sample from drain plug as deposits accumulate in this area 4. Clean area around petcock, filter tube, oil pan, barrel bung or drain plug as the case may be to prevent contamination of the oil sample 5. Take the sample before top ups so that it is representative of the condition at the time of sampling. In case if sample is taken after adding make - up oil, run the engine for some time before drawing sample. 6. The samples may be drawn the same way each time to assure comparable results as far as possible 7. Discard the initial volume of oil from the sampling line to be sure the sample is representative. 8. Seal the sample container and label properly before sending it to the designated laboratory. 9. Obtain and keep record of Sample date, Odometer reading, Distance /hours since last oil change, sump capacity, fuel /oil consumption rates etc Valvoline Technical Services Page 8