What Is a Lubricant — and What It Is Not

A lubricant is any substance placed between two moving surfaces to reduce friction, transfer heat away from the contact zone, and protect surfaces from wear, corrosion, and contamination. In industrial and workshop applications, lubricants are the difference between machinery that runs reliably for years and machinery that destroys itself from the inside.

But lubricant is also one of the most misused terms in Australian workshops. WD-40 is not a lubricant — it is a penetrating fluid and water displacer. Engine oil is not a substitute for gear oil. Hydraulic oil is not interchangeable with way oil, even if the viscosity grade matches. These substitutions are made daily in workshops across Australia, and they cause premature component failures that look like mechanical problems but are actually lubrication problems.

This guide covers every major industrial lubricant type: what it does, when to use it, what grade to select, and — critically — what not to substitute for it.

The 4 Types of Lubricants

Lubricants fall into four broad categories, each with distinct properties and applications. Understanding the category helps you identify the right product before drilling into the specific grade or formulation.

1. Oils (Liquid Lubricants)

The largest and most varied category. Oils are liquid at operating temperature, flow into contact zones under pressure or gravity, and are circulated, filtered, and replaced. Industrial oils include hydraulic oil, gear oil, compressor oil, cutting oil, chain oil, way oil, turbine oil, and general machine oil — each a distinct product type with its own additive package. Oils are used where the system can contain a liquid, where heat removal is important, or where components are close-tolerance and require a thin, fluid film.

2. Greases (Semi-Solid Lubricants)

Grease is base oil — typically ISO VG 100–460 — held in suspension by a thickener (soap or polymer matrix). The thickener holds the oil at the contact point and releases it gradually under heat and pressure. Grease is used where oil would migrate away from the bearing or contact zone, where re-lubrication intervals are long, where the application is exposed to contamination from water or dust, or where sealing against ingress is required. Common thickener types include lithium (most common), calcium, lithium complex, calcium complex, and polyurea — compatibility between different thickener types varies and mixing should be avoided.

3. Dry Lubricants

Solid lubricants that reduce friction without a liquid carrier. The three most common are PTFE (polytetrafluoroethylene), graphite, and molybdenum disulphide (MoS2). Dry lubricants are used where liquid lubricants would attract or retain contamination (food processing, clean rooms, textile machinery), at temperatures beyond the range of mineral or synthetic oils, or as an additive within oils and greases to enhance extreme pressure performance. PTFE spray lubricants are widely used in Australian workshops for slide mechanisms, hinges, and guide rails where oil would attract dust.

4. Penetrating and Water-Displacing Fluids

Products such as WD-40, CRC 5-56, and Inox MX3 are not lubricants in the industrial sense — they are penetrating fluids designed to displace water, infiltrate corroded threads, and free seized components. They evaporate and leave minimal lasting film. The confusion arises because these products do reduce friction momentarily, which is often mistaken for lubrication. Use penetrating fluids to free corroded parts, then follow up with an appropriate oil or grease for sustained lubrication. Never rely on WD-40 as the sole lubricant for a bearing, chain, gearbox, or hydraulic component.

Hydraulic Oil

Hydraulic oil transmits power in hydraulic systems — pressing, lifting, clamping, steering, and actuating. It must maintain a consistent viscosity across operating temperatures, protect pump internals from wear under pressure, resist oxidation and foam formation, and remain compatible with seals and hoses.

Hydraulic oil is graded under the ISO VG system. ISO VG 46 is the most common grade for Australian industrial and mobile equipment. ISO VG 32 suits machine tools and cold-climate applications; ISO VG 68 suits high-temperature or high-pressure systems. Most hydraulic oil sold in Australia is AW-rated (anti-wear), containing ZDDP additives to protect vane, piston, and gear pump internals. Browse the hydraulic oil range at AIMS Industrial for current stock in ISO VG 32, 46, and 68.

For a complete guide to ISO VG grades, AW vs HVI, zinc-based vs zinc-free, and hydraulic oil selection by application, see the AIMS Hydraulic Oil Guide.

Gear Oil

Gear oil lubricates gearboxes, differentials, worm drives, and final drive assemblies. The fundamental difference from hydraulic oil is the additive package: gear oil contains extreme pressure (EP) additives — typically sulphur-phosphorus or borate chemistry — that activate under the high contact pressures between meshing gear teeth, forming a sacrificial protective film that prevents welding and scoring.

Gear oil is graded in two parallel systems:

• ISO VG: The same viscosity scale used for industrial oils. Gear oils typically run ISO VG 68 to ISO VG 460 depending on application — far heavier than hydraulic oil grades.
• AGMA (American Gear Manufacturers Association): A classification system widely used in Australian industrial gearbox specifications. AGMA 2 ≈ ISO VG 100; AGMA 4 ≈ ISO VG 150; AGMA 6 ≈ ISO VG 320; AGMA 8 ≈ ISO VG 680.

For a complete cross-reference of ISO VG grades alongside SAE engine and gear oil equivalents, see the ISO VG viscosity chart.

The GL rating (API GL classification) defines EP performance level:

Common mistake: filling an industrial gearbox with hydraulic oil because it's in the same ISO VG range. Hydraulic oil has no EP protection. Gear tooth scuffing and eventual tooth failure follows — often attributed to mechanical fault rather than the correct cause. Browse gear oils and industrial lubricants at AIMS Industrial.

For a complete guide to ISO VG and AGMA grades, GL-4 vs GL-5 EP ratings, worm gear oil selection, and mineral vs synthetic options, see the AIMS Gear Oil Guide.

Compressor Oil

Compressor oil is one of the most incorrectly specified lubricants in Australian workshops and manufacturing facilities. The temptation to use what's on the shelf — hydraulic oil, engine oil, or general machine oil — is understandable when a compressor needs a top-up on a Saturday morning with no industrial supplier open. The consequences, however, are serious.

Why Compressor Oil Is Different

Compressed air reaches temperatures of 80–120°C or higher in the compression chamber. At these temperatures, standard mineral oils oxidise rapidly, forming varnish deposits that coat internal surfaces, restrict oil flow, and eventually block the oil separator. In a rotary screw compressor, varnished oil separators cause oil carryover into the air system — contaminating downstream processes and damaging air tools, pneumatic cylinders, and instrumentation.

Compressor oils are formulated with low-residue base stocks and inhibitor packages specifically designed to resist oxidation at compression temperatures. They are also formulated to separate from compressed air efficiently, minimising oil carryover.

Reciprocating vs Rotary Screw Compressor Oil

Food-Grade Compressor Oil

Australian food and beverage manufacturers, pharmaceutical producers, and food packaging operations often require compressor oil that meets food-safe requirements. ISO 21469 certification (formerly H1 rating from NSF International) indicates the oil is acceptable for incidental contact with food. Food-grade compressor oils use USP white oil or PAO base stocks with food-safe additive packages. If your compressed air system could contaminate product — directly or through leaks — food-grade compressor oil is mandatory. View food-safe and specialty lubricants at AIMS Industrial.

Cutting and Machining Oil

Cutting oil serves three functions simultaneously: lubricate the cutting edge, cool the workpiece and tool, and flush away swarf. Getting the cutting fluid right extends tool life significantly, improves surface finish, and reduces heat-induced dimensional error in precision work.

Types of Cutting Fluid

Neat Cutting Oil

Used undiluted. Provides maximum lubrication at the cutting edge, making it the preferred choice for slow, heavy operations where heat generation is limited but cutting forces are high: deep hole drilling, tapping, threading, broaching, gear hobbing, and grinding with form wheels. Neat cutting oil provides excellent tool life in these applications. It is less effective at cooling than water-based alternatives, so it is less suitable for high-speed operations that generate significant heat.

Soluble (Emulsifiable) Oil

Concentrated oil that is diluted with water — typically at ratios of 1:20 to 1:40 — to form a milky white emulsion. The water content provides significantly better cooling than neat oil, making soluble oil the standard cutting fluid for general turning, milling, drilling, and surface grinding in Australian machine shops. The correct concentration matters: too dilute (>1:40) reduces lubrication and corrosion protection; too concentrated (<1:15) reduces cooling effectiveness and increases cost without benefit. Measure concentration with a refractometer and adjust regularly.

Semi-Synthetic Coolant

A blend of mineral oil emulsion and synthetic components. Provides better stability than soluble oil (less prone to bacterial growth and emulsion separation), longer sump life, and improved surface finish in many applications. Used across a wide range of operations as a premium alternative to soluble oil.

Fully Synthetic Coolant

Oil-free, water-based. Provides excellent cooling and very long sump life. Most suitable for high-speed machining of aluminium and non-ferrous metals, and for grinding operations. Some materials — particularly cast iron and certain tool steels — benefit from the lubrication provided by oil-containing coolants; check compatibility with your workpiece material.

Browse cutting oils and machining coolants at AIMS Industrial.

Chain Lubricant

Chain lubrication is one of the most frequently neglected maintenance tasks in Australian industrial facilities — and one of the most consequential. A dry or poorly lubricated roller chain wears at the pin and bushing interface (not the side plates or rollers that are visually obvious), elongates, and eventually jumps sprocket teeth or fails under load.

What Chain Lubricant Must Do

• Penetrate to the pin-bushing interface — this is where wear actually occurs, not on the outer surface of the link plates. A lubricant that only coats the outside of the chain provides minimal wear protection.
• Resist fling-off at operating speed — light oils fling off centrifugally on fast-moving chains. Chain lubricants are formulated with the correct viscosity and tackiness additives to adhere to the chain at speed.
• Protect against corrosion — particularly on chains in outdoor, washdown, or humid environments.

Chain Lubrication Methods

Typical ISO VG grades for chain lubrication: ISO VG 68–100 for general-purpose industrial chains; ISO VG 150 for slow-speed, high-load chains; lighter grades for high-speed drives where penetration is prioritised. Always check the chain manufacturer's lubrication specification.

Browse chain lubricants at AIMS Industrial.

For a complete guide to chain lubricant types — wet, dry, wax and industrial oils — selection criteria and application methods, see the AIMS Chain Lube Guide.

Way Oil (Slideway Oil)

Way oil is one of the least understood industrial lubricants — and one of the most precisely specified. Machine tool slideways (lathes, mills, grinders, machining centres) require a lubricant with a specific property not found in any other oil category: a tackiness (anti-stick-slip) additive.

The Stick-Slip Problem

When a machine slide moves slowly — during fine finishing cuts, for example — the friction between the slide and the way surface can cause intermittent sticking and slipping: the slide grabs, releases, grabs again. This produces chatter marks on the workpiece surface and dimensional inaccuracy. The tackiness additive in way oil forms a film that transitions smoothly from static to dynamic friction, eliminating the stick-slip behaviour.

An oil without this additive — including hydraulic oil, gear oil, or general machine oil of the same ISO VG grade — will not prevent stick-slip, regardless of viscosity. This is the most important selection criterion for way oil and cannot be compromised.

Way Oil Grades

Way oil is also used in EDM (electrical discharge machining) machines, gear hobbers, and some jig borers. Always confirm the machine manufacturer's specification — the ISO VG grade and sometimes a specific product approval may be required. Browse way oils and machine tool lubricants at AIMS Industrial.

Cross-Contamination: The Risk Nobody Talks About

Using the wrong lubricant in the wrong application is the most common cause of premature lubricant-related failures in Australian industry — and the most preventable. Cross-contamination can be accidental (wrong drum grabbed in the dark, unlabelled dispensing equipment) or intentional ("it's the same viscosity, it'll be fine"). Neither produces acceptable outcomes.

Contamination prevention is straightforward: label all lubricant storage containers and dispensing equipment clearly with product name and ISO VG grade, store different lubricants in dedicated colour-coded containers, and establish a one-way rule — once a dispensing container has been used for a specific product, it only ever carries that product.

How to Choose the Right Industrial Lubricant

A four-step decision process covers the large majority of Australian industrial lubrication requirements:

Step 1: Identify the Application

What is being lubricated? Hydraulic system → hydraulic oil. Gearbox or gear drive → gear oil. Air compressor → compressor oil. Machine tool slideway → way oil. Roller chain or drive chain → chain lubricant. Cutting or machining operation → cutting fluid. Open bearing or pivot → grease or general machine oil.

Step 2: Check the OEM Specification

The equipment manufacturer's service manual is always the primary reference. It specifies the oil type, ISO VG grade, performance classification (GL-4, GL-5, food-safe ISO 21469, compressor-specific), and change interval. Following the OEM specification protects warranty, ensures compatibility with seals and materials, and uses the grade validated for the equipment's design operating conditions.

Step 3: Assess Operating Conditions

If the OEM specification is unavailable: determine the ambient temperature range (affects ISO VG grade selection), operating load and speed (affects EP requirement and viscosity), and any special requirements — food contact compliance, fire resistance, extreme temperature, extended drain interval. Higher temperature generally requires a higher ISO VG grade; higher load generally requires EP additives.

Step 4: Match Additive Requirements

ISO VG grade alone is not enough. An ISO VG 68 hydraulic oil and an ISO VG 68 gear oil are entirely different products. Identify the required additive type: AW (anti-wear, for hydraulic systems), EP (extreme pressure, for gearboxes), anti-stick-slip (for slideways), low-residue (for compressors), or food-safe (for food-contact applications).

5 Common Industrial Lubrication Mistakes

1. Using Hydraulic Oil for Everything

Hydraulic oil is AW-rated and widely available — which makes it the default top-up fluid in many Australian workshops. It works fine in hydraulic systems. In a gearbox it provides no EP protection. In a compressor it forms varnish. On a slideway it causes stick-slip. Identify the application before reaching for the drum.

2. Treating WD-40 as a Lubricant

WD-40 is excellent at what it does: displacing water, loosening seized fasteners, and providing short-term corrosion protection. It evaporates within hours. Using it as a chain lubricant, bearing lubricant, or slideway oil accelerates wear because it removes the existing lubricant film while depositing almost nothing in return. Use it to free parts; follow with a proper lubricant.

3. Mixing Incompatible Oils

Particularly: zinc-based and zinc-free hydraulic oils (sludge risk); mineral and synthetic oils without flushing (additive incompatibility); different brands' gear oils without checking additive compatibility; and mixing any grease types without confirming thickener compatibility. When switching products, drain, flush, and degrease where feasible — see the Industrial Degreaser Guide for solvent selection when switching lubricant types.

4. Ignoring the OEM Specification Beyond ISO VG Grade

Two oils of the same ISO VG grade can be entirely different products with entirely different additive packages. The ISO VG number tells you the viscosity; it says nothing about EP level, tackiness, oxidation stability, or compressor suitability. Always check the full OEM specification — not just the grade number.

5. Running Past Change Intervals Without Oil Analysis

Change intervals are based on typical conditions. If your equipment runs hotter than normal, handles higher loads, operates in a dusty or humid environment, or is critical to production continuity, oil analysis gives you the actual condition of the oil rather than a time-based estimate. For hydraulic and gear systems in high-duty applications, oil analysis pays for itself many times over in avoided pump and gearbox replacements.

Frequently Asked Questions

What is a lubricating oil?

A lubricating oil is a refined petroleum or synthetic fluid used to reduce friction between moving surfaces, transfer heat away from contact zones, and protect metal from corrosion and contamination. Lubricating oils are distinguished from greases (semi-solid), dry lubricants (PTFE, graphite, molybdenum disulphide), and penetrating fluids such as WD-40, which serve different purposes and are not true lubricants.

What are the 4 types of lubricants?

The four main categories of lubricants are: (1) Oils — liquid lubricants including hydraulic oil, gear oil, compressor oil, cutting oil, chain oil, and way oil, each formulated for specific applications; (2) Greases — semi-solid lubricants consisting of base oil held in a thickener, used where oil would migrate away from the contact point; (3) Dry lubricants — PTFE, graphite, and molybdenum disulphide, used in high-temperature environments, clean rooms, or where liquid lubricants would attract contamination; and (4) Penetrating and water-displacing fluids — products such as WD-40, CRC, and Inox MX3, which loosen corroded parts and displace moisture but do not provide lasting lubrication.

Is WD-40 a lubricating oil?

No. WD-40 stands for Water Displacer, formula 40. It is a penetrating fluid designed primarily to displace water, loosen corroded or seized fasteners, and provide short-term corrosion protection. WD-40 evaporates and leaves minimal lasting lubricating film. For ongoing lubrication of bearings, chains, gearboxes, slideways, or any component requiring sustained oil film, use a purpose-formulated lubricating oil or grease. WD-40 is a useful workshop tool — but not as a substitute for proper lubrication.

What are some examples of lubricating oils?

The main industrial lubricating oil types are: hydraulic oil (power transmission and pump protection), gear oil (gearboxes, differentials, final drives), compressor oil (reciprocating and rotary screw compressors), cutting oil (machining, drilling, threading, grinding), chain oil (roller chain drives, conveyor chains), way oil (machine tool slideways), and machine oil (general-purpose light lubrication). Each is formulated with a specific additive package for its application — they are not interchangeable.

What is the difference between hydraulic oil and gear oil?

Hydraulic oil is formulated for power transmission and hydraulic pump protection, with anti-wear (AW) additives — typically zinc-based — that protect pump internals. Gear oil is formulated for the sliding contact between gear teeth and contains extreme pressure (EP) additives — usually sulphur-phosphorus chemistry — that activate under the high contact pressures of meshing gears. EP additives would cause corrosion in hydraulic pumps; AW additives provide insufficient protection for gear tooth contact. They must not be substituted for one another.

Can I use hydraulic oil on my machine's slideways?

No. Machine tool slideways require way oil, which contains a tackiness additive (stick-slip inhibitor) that prevents judder and chatter as the slide moves. Hydraulic oil of the same ISO VG grade does not contain this additive. Using hydraulic oil on ways results in inconsistent slide movement, vibration, and poor surface finish on machined parts. Always use a dedicated way oil — ISO VG 32, 68, or 220 depending on the machine manufacturer's specification.

What compressor oil should I use for a rotary screw compressor?

Use a compressor oil specifically formulated for rotary screw compressors — either mineral ISO VG 46 for standard duty or synthetic compressor oil for extended drain intervals (typically 4,000–8,000 hours versus 500–1,000 hours for mineral oil). Do not use hydraulic oil, engine oil, or general machine oil. These form varnish and carbon deposits in the compressor's air end and oil separator, causing overheating, loss of efficiency, and premature failure. Always follow the compressor manufacturer's oil specification.

What is EP gear oil and when do I need it?

EP stands for Extreme Pressure. EP gear oils contain additives — typically sulphur, phosphorus, or borate compounds — that activate under the high contact pressures between gear teeth, forming a sacrificial protective film that prevents welding and scoring. The GL rating system defines EP performance: GL-4 is used in most manual gearboxes and axles; GL-5 provides higher EP protection for hypoid gears (common in rear differentials). Important: GL-5 can be incompatible with yellow metals (brass, bronze) found in some older industrial gearboxes and synchromesh transmissions — check the OEM specification before using GL-5 where GL-4 is specified.

What is the difference between neat cutting oil and soluble oil?

Neat cutting oil is used undiluted and provides maximum lubrication for heavy or slow machining operations — deep hole drilling, threading, broaching, and gear cutting. It provides excellent tool life but less cooling than water-based alternatives. Soluble (emulsifiable) oil is diluted with water, typically at ratios of 1:20 to 1:40, to form a milky white emulsion that provides significantly better cooling alongside lubrication. Soluble oil is the most common cutting fluid in Australian machine shops, suited to general turning, milling, drilling, and surface grinding. Semi-synthetic and fully synthetic coolants offer similar function with improved stability and longer sump life.

Can I mix different industrial lubricants?

As a general rule, no. Even within the same lubricant type, mixing oils from different manufacturers or different additive packages can cause incompatibility — sludge formation, foaming, emulsification, or reduced additive performance. Mixing across types is always wrong: gear oil in a hydraulic system introduces EP chemistry that corrodes pump metals; compressor oil in a gearbox may lack EP protection; different grease thickener types (lithium and calcium complex, for example) can collapse when mixed. When changing lubricants, drain and flush where possible and refill with the new product.

What lubricant does a roller chain need?

Roller chains require an oil with sufficient penetration to reach the pin-bushing interface (where wear actually occurs) and enough viscosity or tackiness to resist fling-off at operating speed. ISO VG 68 to ISO VG 150 mineral chain oil is standard for most industrial conveyor and drive chains, depending on speed and operating temperature. Aerosol chain lubricants are convenient for maintenance but carry less volume than drip or bath lubrication on high-cycle chains. Do not use chainsaw bar oil on roller chains — bar oil is specifically formulated for high-speed bar-and-chain contact and is not appropriate for pin-bushing lubrication.

How do I know which lubricant is right for my equipment?

Start with the equipment manufacturer's service manual — it will specify the oil type, ISO VG grade, performance classification (GL-4, GL-5, food-safe ISO 21469, compressor-specific), and change interval. If the manual is unavailable: identify the application type (hydraulic system, gearbox, compressor, cutting operation, chain drive, or machine slideway); determine the operating temperature range and load conditions; and check for special requirements such as food contact compliance, fire resistance, or extended drain intervals. Match these to the appropriate oil type and grade using the selection guide in this article. When in doubt, contact the lubricant supplier's technical team — most Australian industrial suppliers offer free application support.

Shop Industrial Lubricants at AIMS Industrial

AIMS Industrial stocks a comprehensive range of industrial lubricants — hydraulic oil, gear oil, compressor oil, cutting oil, chain lubricant, way oil, and specialty lubricants — from leading Australian and international brands. Browse the full lubrication range including hydraulic oil in ISO VG 32, 46 and 68 in 5L, 20L, and drum quantities. For dispensing lubrication oils from 20L/60L/205L drums see the Oil Pump & Drum Pump Guide covering lever, rotary, air-operated and battery pumps. For equipment-specific guidance, see our detailed hydraulic oil guide covering ISO VG grades, AW vs HVI, and selection by application.