Mechanical Systems

Lubricant Fundamentals 211

Lubricant Fundamentals describes different types of lubricants and appropriate uses for them in machines and mechanical systems. A variety of machines require proper lubrication in order to function safely and efficiently. Lubricants help prevent wear and ensure operational efficiency by decreasing friction between components in contact. Common industrial lubricants include oil, grease, and solid lubricants.

Machine operators and maintenance personnel must understand basic lubricant properties so they can select, apply, and replace lubricants properly. They must also recognize signs of improper lubrication and be aware of proper maintenance, storage, and safety practices for lubricants. After completing this course, users will understand the advantages and disadvantages of different types of lubricants, their operational properties, and procedures for proper lubrication.

  • Difficulty Intermediate

  • Format Online

  • Number of Lessons 21

  • Language English


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Course Outline
  • Mechanical Systems and Lubrication
  • Lubrication Regimes: Boundary and Mixed-Film
  • Lubrication Regimes: Full-Film
  • Lubricant Properties
  • Review: Lubrication Basics
  • Oil
  • Oils: Advantages and Disadvantages
  • Grease
  • Grease: Advantages and Disadvantages
  • Additives
  • Solid Lubricants
  • Solid Lubricants: Advantages and Disadvantages
  • Review: Oil, Grease, and Solid Lubricants
  • Proper Lubricant Selection and Application
  • Lubricant Delivery Methods
  • Determining Lubrication Frequency
  • Effects of Overlubrication
  • Review: Proper Lubrication Methods
  • Lubricant Maintenance and Storage
  • Lubricant Safety
  • Review: Proper Lubrication, Maintenance, Storage, and Safety
  • Describe the role of lubrication in mechanical systems.
  • Distinguish between boundary and mixed-film lubrication.
  • Contrast the different forms of full-film lubrication.
  • Describe general properties of lubricants.
  • Describe the primary types of lubricating oils used in industry.
  • Distinguish between the advantages and disadvantages of lubricating with oils.
  • Describe grease used for lubrication.
  • Distinguish between the advantages and disadvantages of lubricating with grease.
  • Describe types of additives used in lubricants.
  • Describe the various types of solid lubricants used in lubrication.
  • Distinguish between the advantages and disadvantages of using solid lubricants.
  • Describe important considerations for properly selecting and applying lubricants.
  • Describe various methods of applying lubricants.
  • Describe various factors that affect lubrication frequency.
  • Describe the effects of overlubrication.
  • Describe proper maintenance and storage procedures for lubricants.
  • Describe important safety considerations for working with lubricants.
Vocabulary Term


A corrosive chemical compound. Acid can build up in oil-based lubricants and lead to oil sludge.


A substance added in small amounts to another substance or material. Additives can improve the various properties of lubricants.

anti-foaming agents

An additive used to reduce the formation of foam in a lubricant. Anti-foaming agents help reduce lubricant contamination and improve lubricant function.


An additive that helps prevent oxidation. Antioxidants can extend the life of a lubricant.


A microscopic peak on a surface. When objects are in motion, contact between asperities causes friction.

base oil

Refined oil that contains no additives. Base oils for industrial lubricants can either be mineral or synthetic oils.


A friction-reducing device that allows one moving part to glide past another moving part. Bearings operate using a sliding or rolling mechanism.

boundary lubrication

A lubrication regime in which a very thin layer of fluid-film separates two surfaces in contact. Boundary lubrication, or thin-film lubrication, is unable to completely prevent surface-to-surface contact and allows for the creation of friction and wear.


A shaft that features one or more irregularly shaped components, called cams, of various sizes. Camshafts are powered by crankshafts in internal combustion engines and control the timing and flow of fuel, air intake, and exhaust.

centralized lubrication system

An automated lubricant delivery method that lubricates multiple machine parts at once. Centralized lubrication systems can deliver either oil or grease to machine components.


Undesirable friction that occurs between fluids. Churning is often the result of overlubrication.


A material made by mixing together two or more of the following groups: metals, plastics, and ceramics. In a composite, all the materials retain their respective characteristics.

computer numerical control

CNC. A programmable control system that uses mathematical data to execute program instructions and direct the movement of a machine and its components. Computer numerical control is a much quicker and more precise form of machine operation than manual machine operation.


To transfer energy, such as heat or electricity. Lubricants which conduct heat can help cool machine components.


Damaging foreign material such as dirt or debris that causes wear to machine components. Contaminants may cause a loss of efficiency or a breakdown in a mechanical system.


The presence of foreign substances in a lubricant. Contamination can cause premature wear and lead to operational problems.


The gradual deterioration of a material due to atmosphere, moisture, chemicals, or other agents. Corrosion often appears as rust.


A rotating shaft with offset sections that converts reciprocating linear motion into rotary motion. Crankshafts are used to power the pistons in an internal combustion engine.

crude oils

Unrefined petroleum oil. Crude oil is often refined and mixed with additives for use as a lubricant.


An additive used to separate undissolved droplets of one liquid from within another liquid. Demulsifiers are commonly used in the oil refining process to remove water.


A substance with chemical components that acts as a cleaning agent. Detergents are added to oils to help break down contaminants and improve corrosion resistance.


A period of time when production stops, often due to mechanical failure or maintenance needs. Downtime can be planned or unplanned.

drip feed

A gravity lubrication system that delivers oil to a lubrication point automatically through a nozzle. Drip feeds can be switch on or off and can be adjusted to change the flow rate of the of the oil.

dry lubricant

A nonflowing substance used to reduce friction between two surfaces in relative motion. Dry lubricants are also referred to as solid lubricants.

elastic deformation

A temporary change in the shape of an object or material due to the application of force or stress. When a material experiences elastic deformation, it returns to its original shape once the stress is removed.

elastohydrodynamic lubrication

EHL. A form of full-film lubrication in which the fluid-film is created by extreme pressure exerted on the lubricant at nonconformal contact points due to the rolling motion of components. Elastohydrodynamic lubrication occurs when extreme pressure thickens the lubricant's consistency and causes the surfaces in contact to expand.

extreme pressure additives

Any substance that is added to a material to increase the material's effectiveness as a lubricant under extreme conditions. Extreme pressure additives are often used in heavy-duty industrial applications.


A device that holds two or more objects together. Common fasteners include screws, nuts, and bolts.


Processed to remove contaminants and debris. Filtered oil can often be recirculated through a system for reuse.

fire point

The temperature at which a fluid, such as oil, will ignite on the surface and continue to burn. The fire point of a lubricant is just beyond its flash point.


Easily ignited or set on fire. Flammable liquids have a flash point below 100° F (38° C) and can typically ignite at room temperature.

flash point

The lowest temperature at which a liquid's vapors will ignite. Oils with low flash points pose a fire safety risk in high-temperature applications.

fluid-based lubricants

Natural or man-made lubricants which have a liquid base, such as natural oils. Fluid-based lubricants used in industry include oils as well as greases, which contain base oils.


The layer of fluid in a lubricant that fills the space between two surfaces to reduce or eliminate surface contact. The fluid-film's thickness and the amount of surface contact the lubricant eliminates determines its lubrication regime.


The accumulation of air bubbles in a liquid caused by trapped air. Foam can lead to lubricant contamination and reduced lubricant efficiency.


An influence, like a push or a pull, that produces a change in an object's motion or state of rest. Forces have specific directions and magnitudes.


A force that resists motion between two components that are in contact with each other. Friction generates heat and increases wear between components.

full-film lubrication

A lubrication regime that occurs when a thick layer of fluid-film completely separates and prevents contact between surfaces. Full-film lubrication is characterized by low friction and no wear.


A round or cylindrical mechanical component with teeth that is used to transmit power. Gears are designed to mesh with one another in order to alter the speed, torque, or direction of mechanical energy.


A classification that describes the thickness of industrial lubricating grease. Grades of grease range from 000 to 0 on the NLGI scale.

grade 2

The most commonly used grade of industrial lubricating grease. Grade 2 grease has a medium-soft consistency.


A soft, black form of carbon that can be used as a lubricant. Graphite is usually sold as a spray or powder for lubrication.

gravity lubrication system

A type of lubricant delivery system that uses individual lubricant reservoirs from which lubricant is distributed to machine parts. Gravity lubrication systems typically use drip feeds or wick feeds to deliver lubricant.


A semisolid substance composed of oil and a chemical soap or other additive. Grease is commonly used as an industrial lubricant.


A machine that uses an abrasive to wear away at the surface of a workpiece. Grinders provide an efficient way to shape and finish metals and other materials.

hand-operated gun

A device used to apply lubricant manually to machines. Hand-operated guns are used for both oil and grease.

hydrodynamic lubrication

HDL. A form of full-film lubrication in which the fluid-film separating two surfaces is created and maintained by the pressure exerted by the surfaces' movement. Hydrodynamic lubrication is an ideal type of lubrication, but it can be difficult to maintain.

hydrostatic lubrication

HSL. A form of full-film lubrication in which the fluid-film separating two surfaces is created by a pressurized lubricant that is constantly supplied by an external source. Hydrostatic lubrication is effective in machines that do not maintain constant motion.

journal bearings

A friction-reducing device that allows one moving part to glide past another moving part. Journal bearings often use hydrodynamic lubrication.

lithium soap

A chemical soap derived from lithium. Lithium soap is often used as a thickening agent for lubricants.


The amount of force or pressure placed on a component or system. Heavy loads can change the properties of lubricants.


A substance used to reduce friction between two surfaces in relative motion. Common industrial lubricants include oil and grease.


The application of a slippery substance, such as oil or grease, between two moving surfaces in contact with each other. Lubrication minimizes friction, heat, and wear.

lubrication point

The location on a machine or machine component to which lubricant is delivered. Lubrication points may be lubricated by hand or automatically using a centralized lubrication system.

lubrication regimes

Categories that describe the functional status of an oil at any point during machine operation. Lubrication regimes are determined by the degree of contact between surface asperities allowed by the oil's fluid-film.


The ability of a fluid to reduce friction and provide lubrication. High lubricity in a hydraulic fluid indicates an effective lubricant.


A device consisting of one or more parts that transform energy into motion. Machines are used to transmit or modify force and motion so as to accomplish some form of useful work.


The necessary and basic support and repair of machines. Maintenance includes tasks such as lubricating, adjusting, and replacing parts.

mechanical system

A collection of machines functioning together to perform useful work. Mechanical systems include belt drives, gear drives, and chain drives.

mineral oils

A naturally occurring oil derived from petroleum. Mineral oil is used as both a lubricant and coolant.

mixed-film lubrication

A lubrication regime in which the fluid-film separating two surfaces is slightly thicker than it is in boundary lubrication but still allows for some surface-to-surface contact. Mixed-film lubrication typically is a transitional stage that occurs after boundary and before full-film lubrication as a machine's speed increases or a load decreases.

molybdenum disulfide

A mineral compound that is used as a solid lubricant. Molybdenum disulfide is similar in appearance to graphite.

naphthenic crude oils

Base oils that contain very low levels of paraffin wax. Naphthenic oils are less stable at high temperatures than paraffinic oils but also have lower pour points.

National Lubricating Grease Institute

NLGI. A non-profit organization that establishes international standards for lubricating grease. The National Lubricating Grease Institute is a membership organization made up mainly of manufacturers of industrial grease.


Occurring in nature and not human-made. Natural lubricants include mineral, plant-based, or animal-based oils.

NLGI scale

A scale created by the National Lubricating Grease Institute to measure the viscosity of industrial grease. The NLGI scale ranges from 000 to 6, with 000 being the most fluid grease and 6 the most solid.

nonconformal contact

Contact between two surfaces that is characterized by very small, high-pressure contact points. Nonconformal contact indicates that the surfaces in contact do not fit together evenly or snugly.


A slippery fluid commonly used as a lubricant. Both mineral and synthetic oils are used in industrial applications.

oil circulation system

A centralized lubrication system that filters and recirculates oil through a system after lubrication for reuse. Oil circulation systems are more complex and can lower long-term costs of lubrication.

oil mist system

A lubricant delivery method that pipes oil to desired locations and dispenses the oil with a spray nozzle. Oil mist systems cool and lubricate many machine components at once.

oil pump

A component in a lubrication system that pressurizes and continually supplies oil. Oil pumps are sometimes used to achieve hydrostatic lubrication.

oil sludge

A form of contamination that can decrease the effectiveness of a lubricant. Oil sludge is gummy liquid matter that can form in the reservoir containing the oil.


The application of too much lubricant to a machine component. Overlubrication can lead to machine malfunction.


A chemical reaction involving the addition of oxygen, the removal of hydrogen, or the removal of electrons from a lubricant. Oxidation weakens and degrades a lubricant.

oxidation stability

The ability of a fluid, such as oil, to maintain its integrity over time and resist oxidation. Oxidation stability helps protect against corrosion and rust.

paraffinic crude oils

Base oils that contain high levels of paraffin wax. Paraffinic oils perform well at higher temperatures but have a higher pour point since they contain wax.


A lubricant with a thick, sticky consistency. Pastes are solid lubricants that can be mixed in with other materials or spread on a surface of an object, such as the surface of a cutting tool.

pounds per square inch

psi. A unit of pressure used in the English system. The pounds per square inch unit measures the amount of load pressure that is applied over an area of one square inch.

pour point

The lowest temperature at which a liquid remains fluid. Lubricants with lower pour points are suitable for machine applications at lower operating temperatures.

premature wear

The unexpected erosion of material caused by excess friction. Premature wear can result in high costs, downtime, and even injury.


The application of force or stress upon an object or substance, which experiences a change in properties as a result. Pressure exerted upon a lubricant creates a fluid-film of various thicknesses that separates two surfaces.


pounds per square inch. A unit of pressure used in the English system. The psi unit measures the amount of load pressure that is applied over an area of one square inch.


The groove within an anti-friction bearing that runs along the middle of the inside and outside bearing rings. The raceway provides a path for the bearing's rolling elements.


The main storage container for oil or other type of fluid. A reservoir supplies lubricant in a centralized lubrication system.


A breathing device worn to prevent inhalation of hazardous substances. A respirator may be required when working with chemicals that produce hazardous fumes or debris.

rolling contact

Contact between a rolling component and another surface. Rolling contact produces less friction than sliding contact.

rolling elements

The internal components of an anti-friction bearing that roll along the bearing's raceway to support a load and reduce friction. Rolling elements include balls and cylinders.

rolling-element bearings

A type of bearing using rolling motion to support a load and reduce friction. Rolling-element bearings produce less friction than plain bearings.

Safety Data Sheet

SDS. A form that may accompany a chemical in the workplace if an SDS is not provided. Safety Data Sheets detail the risks, precautions, and first aid procedures associated with a chemical.

safety goggles

Tight-fitting eye protection that completely cover the eyes, the sockets, and the surrounding facial area. Safety goggles offer protection from splashing lubricants, as well as impact, dust, and chips.


An intentional obstruction designed to keep fluids, such as lubricants, inside a system. A seal prevents leakage and contamination.


A substance that has a gel-like texture and is not classified as a fluid or a solid. Industrial grease is classified as a semi-solid.

service life

The length of time a machine or machine component is expected to be in operation before requiring replacement. Service life depends on several factors but can be lengthened by preventive maintenance.


Deforms and separates due to the application of parallel forces or stress. When two surfaces slide against one another without proper lubrication, the stronger surface shears bits of material off of the other surface.


The jarring impact caused by sudden acceleration, deceleration, or collision. Shock can damage machine components, especially if they are not properly lubricated.

shock loads

A type of load that occurs at extreme speed and exerts tremendous amounts of force. Shock loads can damage machine components if the proper lubricant is not used.

sliding contact

Contact between components that slide against each other due to linear motion. Sliding contact produces more friction than rolling contact.

solid lubricant

A nonflowing substance used to reduce friction between two surfaces in relative motion. Common solid lubricants include graphite and molybdenum disulfide.

splash lubrication system

A type of lubrication system in which the teeth of a gear dips into a reservoir of lubricant and transfers the lubricant as it rotates. Splash lubrication systems are often used in enclosed gearboxes.


An elastic device used to dampen and apply force, control motion and vibration, and store energy. Springs are used in many mechanical systems to aid in the storage and transfer of energy.


Artificial, human-made, and not of natural origin. Synthetic lubricants are often manufactured from chemicals and additives.

synthetic oils

A lubricant consisting of chemical compounds that are artificially made. Synthetic oils are widely available and can be manufactured in part by using chemically modified petroleum components.


A proprietary solid lubricant used to coat surfaces. Teflon is commonly used to reduce friction between two moving components.

thickening agent

An additive used to increase a lubricant's viscosity. Thickening agents are combined with oil to produce grease.

thin-film lubrication

A lubrication regime in which a very thin layer of fluid-film separates two surfaces in contact. Thin-film lubrication, or boundary lubrication, is unable to completely prevent surface-to-surface contact and allows for the creation of friction and wear.


A long, spiral ridge that winds down the length of a cylindrical part. Threads are found on screws and other types of fasteners.


The application of too little lubricant, or the failure to replenish lubricant when it recedes below the appropriate level. Underlubrication results in excess friction and heat, which can lead to machine failure.


A gas formed by boiling or evaporating a liquid. Lubricant vapors will briefly ignite when the lubricant reaches its flash point.


A property that describes a fluid's resistance to flow. The viscosity of a fluid decreases as temperature increases.

viscosity improvers

An additive used to improve the viscosity index of a lubricant. Viscosity improvers help oils retain viscosity levels at higher temperatures.

viscosity index

VI. A measure of a fluid's change in viscosity within a given temperature range. Viscosity index helps determine the temperature range at which a hydraulic fluid can perform.


The erosion of material as a result of friction. Wear typically is caused by two or more objects rubbing or sliding against each other.

wick feed

A gravity lubrication system that delivers oil to a lubrication point through a strip of absorbent material. Wick feeds also filter the lubricant through the absorbent material.


The result of a force applied to an object and the distance through which the force is applied. In an equation, work is force multiplied by distance.