EP Grease Guide: NLGI, Tests & Sourcing | Altonex Global

EP (extreme-pressure) grease is a lubricating grease formulated with additives that build a sacrificial protective film on metal surfaces under heavy, shock, or boundary-lubrication loads, preventing the metal-to-metal welding and scoring that a standard, non-EP grease film cannot withstand. Buyers specify EP grease for chassis pins, open gears, rolling-element bearings, and coupling assemblies on heavy equipment, mining machinery, steel-mill lines, and industrial gear drives — anywhere loads are heavy, shock-prone, or intermittently wet. This guide explains what the NLGI grade on an EP grease label means, which thickener systems are used and how they compare, which ASTM tests actually prove "EP" performance, how dropping point differs from maximum operating temperature, why mixing different thickeners is risky, and what to specify in packaging, export documents, and an RFQ.

What Is EP (Extreme-Pressure) Grease, and Who Uses It?

EP grease contains additives — commonly sulfurized fatty acids or olefins, zinc compounds, or lead-free organosulfur-phosphorus packages — that form a sacrificial film on metal surfaces under heavy, shock, or boundary-lubrication conditions. Some EP products, often marketed as "moly grease," add molybdenum disulfide (MoS₂) as a solid-film boundary lubricant. This film is what prevents metal-to-metal welding and scoring when a standard, non-EP grease would otherwise break down under load.

Typical buyer segments include heavy and off-highway equipment (construction, mining, agricultural machinery), steel mills, cement plants, industrial gear drives and couplings, and chassis, universal-joint, and wheel-bearing assemblies on loaders and dump trucks — applications combining heavy, shock, or vibrating loads with a frequently wet or contaminated environment. This is a general pattern; always confirm fit against the specific bearing or OEM lubrication manual.

EP performance and NLGI consistency are independent properties — a grease can carry any NLGI grade and an EP additive package at the same time. "EP" is not itself a consistency grade; it is confirmed only by the test methods described below.

What Does the NLGI Grade on an EP Grease Label Mean?

NLGI (National Lubricating Grease Institute) grades classify grease consistency, or firmness, by worked penetration under ASTM D217 — current edition D217-21a — measured in tenths of a millimetre (0.1 mm) of cone penetration into the sample. The lower the number, the softer the grease.

NLGI 2 is the dominant grade for EP grease in rolling-element bearings and heavy-equipment chassis service. NLGI 1 or 0 may suit low-temperature or centralized-pumping systems instead — check the equipment OEM's lubrication chart before choosing.

Which Thickener Systems Are Used to Make EP Grease, and How Do They Compare?

The thickener is the gelling structure holding base oil and additives together. Three families matter most to EP grease buyers:

Lithium-soap EP has a dropping point of roughly 190–220°C (ASTM D2265) and a maximum continuous service temperature around 120–130°C, with moderate water resistance. It is the most economical, widely available EP thickener, but compatible only with other lithium-soap greases.

Lithium-complex EP raises the dropping point to roughly 250°C or higher (ASTM D2265), with a maximum continuous service temperature around 150–180°C and moderate-to-good water resistance. It is a premium multi-service EP thickener, common for heavy-duty wheel bearings, industrial bearings, and centralized systems needing both high load capacity and better heat tolerance than plain lithium.

Calcium-sulfonate complex EP has a dropping point above 300°C (ASTM D2265); typical maximum continuous service temperature is around 150–180°C, varying by formulation. Water resistance is outstanding, including salt-water spray and high-pressure water jets. Its calcium-sulfonate overbasing itself provides extreme-pressure, anti-wear, and corrosion-inhibiting properties, often without a separate sulfur/phosphorus EP package — making it a common choice for marine, offshore, mining, and steel-mill environments.

These dropping-point and service-temperature figures are industry-typical, not a specific product's guarantee — confirm actual figures against the supplier's TDS or COA before specifying a grease for a critical application.

What Tests Actually Prove a Grease Is "EP"? Weld Point, Wear Scar, and Timken OK Load Explained

A grease is not "EP" simply because the label says so. Ask for results from named ASTM test methods, because each measures something different:

• 4-ball EP test — weld point and Load-Wear Index (LWI): ASTM D2596-20. Measures the load (kgf) at which a four-ball rig welds under shock/EP loading, plus a Load-Wear Index from a series of loads. A higher weld point means better protection against sudden shock loads. This method does not apply to silicone or silicone-blend greases.
• 4-ball wear test — wear scar diameter: ASTM D2266-23. Measures wear-scar diameter (mm) under a moderate, steady load — an anti-wear (AW) indicator, not an EP indicator. A lower wear scar means better AW performance. The standard's own scope notes this test cannot, by itself, differentiate EP from non-EP greases, and no correlation has been established with actual field service — treat it as one input, never stand-alone EP proof.
• Timken OK Load: ASTM D2509-20ae1. Reports the minimum load (lbf) that causes scoring or seizure of a sliding Timken test block. A higher OK Load means better EP protection under a different geometry than the four-ball rig, and it appears often on industrial/heavy-equipment EP datasheets.

None of these figures represent a specific product's guaranteed performance. Weld point, LWI, wear-scar diameter, Timken OK Load, and dropping point all vary by formulation and batch — request the actual results from the supplier's TDS or COA.

What Is Dropping Point, and Why Is It Not the Same as Maximum Operating Temperature?

Dropping point is the temperature at which grease transitions from semi-solid to liquid, under the specific conditions of ASTM D2265-22 (Dropping Point of Lubricating Grease Over Wide Temperature Range). It is a quality-control and identification parameter — not a use-temperature ceiling.

As a general guideline, realistic maximum continuous service temperature runs 50–100°C below the dropping point, depending on load, speed, relubrication interval, and thickener type — a guideline to verify against the specific supplier's stated operating range, not a formula to apply blindly. Secondary descriptions of this test method also note that above roughly 200°C, dropping point loses correlation with maximum upper operating temperature for conventional soap-thickened greases; treat this as general caution rather than precise engineering text.

How Does Base-Oil Viscosity Affect Which EP Grease to Choose?

Base-oil viscosity — expressed as the ISO VG grade of the base oil, or KV40 in mm²/s — sets film thickness at the contact point, and should match the application's speed and load:

• High speed / light load generally suits a lower-viscosity base oil, roughly ISO VG 46–100 — thinner oil still builds an adequate film at speed, while too-heavy oil causes churning losses and heat.
• Low speed / high load / high temperature — the more typical EP-grease case in heavy equipment, open gears, and slow chassis pivots — generally suits a higher-viscosity base oil, roughly ISO VG 150–460 or higher, to maintain film thickness under boundary/EP conditions.
• NLGI 2 EP grease in standard rolling-element bearings commonly uses ISO VG 100–150; plain/journal bearings and open gears commonly use ISO VG 320–680.

These are general principles — confirm against the bearing or gearbox manufacturer's speed/load chart, and request the specific KV40 or KV100 figure from the supplier's TDS.

Can an EP Grease Be Mixed with a Different Thickener Already in the Bearing?

Warning: EP greases built on different thickener systems can be chemically incompatible — do not mix or change thickener type without first confirming compatibility. Greases from different thickener families should never be combined unless laboratory-confirmed compatible. Mixing incompatible thickeners can cause catastrophic softening, hardening, or structural collapse of the grease within hours, defeating the EP protection entirely — whether topping up an existing bearing or switching to a new EP product line.

• Lithium-soap grease is compatible only with other lithium-soap grease; it is incompatible with lithium-complex, calcium-sulfonate complex, and polyurea.
• Lithium-complex grease is incompatible with plain lithium-soap and with polyurea.
• Calcium-sulfonate complex generally has broader — though still not universal — compatibility with soap-based greases; confirm, never assume.
• Polyurea grease, used in some sealed-for-life or electric-motor-bearing EP-adjacent products, is incompatible with virtually all soap-based greases (lithium, lithium-complex, calcium, calcium-sulfonate complex, sodium, aluminium-complex), and mixing risks catastrophic softening or hardening within hours. This applies before switching any equipment that may already contain polyurea grease — for example, certain sealed motor bearings — to an EP grease.

When changing thickener families on equipment already in service, do not assume compatibility from NLGI grade or EP rating alone. Best practice is either a full purge — running fresh grease through until only new grease exudes — or a documented bench compatibility test before switching.

How Does a Buyer Choose the Right EP Grease for an Application?

Bringing the sections above into a selection checklist:

1. Confirm the load/shock profile — this drives the EP test values needed.
2. Confirm the NLGI grade required by the equipment OEM manual.
3. Confirm the thickener already in service and whether a changeover is planned — apply the incompatibility warning above.
4. Confirm minimum EP/AW values needed — weld point/LWI (ASTM D2596-20), Timken OK Load (ASTM D2509-20ae1), 4-ball wear-scar maximum (ASTM D2266-23) — then request the supplier's TDS/COA for actual figures.
5. Confirm the operating temperature range against dropping point and thickener type, never dropping point alone.
6. Confirm base-oil viscosity fits the speed/load regime.
7. Confirm water/contamination exposure and request water-washout data if relevant (ASTM D1264 method; figures vary by thickener and formulation).
8. Confirm packaging format and minimum order quantity fit the buyer's consumption volume.

This is a decision framework, not a specification — every numeric figure a buyer ultimately relies on should come from the specific supplier's TDS or COA.

What HS Code Applies When Exporting EP Grease?

This is a flag for verification, not a determination. Lubricating greases are most commonly classified under HS heading 3403 ("lubricating preparations... based on lubricants"). Within it, subheading 3403.19 (containing petroleum oils or oils from bituminous minerals) and subheading 3403.99 (other lubricating preparations, not containing petroleum oils) are the subheadings most often cited for mineral- and synthetic-base greases, respectively.

Heading 3403 is generally understood to exclude preparations containing 70% or more by weight of petroleum oils or bituminous-mineral oils; such products may instead fall under HS 2710.19 (other petroleum oils and preparations, not crude). The exact classification depends on the product's actual composition and the destination country's own customs interpretation.

Confirm the exact HS code with a licensed customs broker, or check the destination country's own tariff schedule (for example, the USITC Harmonized Tariff Schedule or the EU TARIC database), before shipping or quoting Incoterms. No single code should be treated as definitively correct for a class of grease products.

What Packaging Formats and Order-Quantity Ranges Are Typical for EP Grease?

EP grease is traded in a standard range of packaging formats:

• 400 g cartridge — polypropylene, DIN 1284 dimensions, typically 12 per case; fits any standard grease gun.
• 1–2 kg tub/sleeve — automotive-aftermarket small-quantity format.
• 5 kg pail — small workshop quantities.
• 18 kg pail — industrial-standard small-bulk format.
• 50 kg drum — mid-size industrial format, typically a UN 1A2 open-head steel drum.
• 180 kg (200 L nominal) open-head drum — bulk industrial standard, UN 1A2 open-head (not the 1A1 closed-head liquid spec) so a follower plate can be used; tare approximately 18 kg, external dimensions roughly 584 mm diameter × 876 mm height.

Minimum order quantities always vary by supplier — the ranges below are industry-typical only, never a guarantee:

Container-loading math — how many 180 kg drums fit a 20' GP or 40' HC container — depends on stacking limits, total weight, and specific gravity; confirm with a freight forwarder rather than an estimated figure.

What Documents Does an EP Grease Export Shipment Need?

A typical EP grease export shipment relies on the following documents:

What Should a Buyer Include in an EP Grease RFQ?

A complete RFQ for EP grease should specify:

1. Application (e.g., heavy-equipment chassis pins, open gears, mining conveyor bearings, industrial gear couplings).
2. NLGI grade required.
3. Thickener system required or preferred (lithium, lithium-complex, calcium-sulfonate complex, or other), including compatibility notes for any grease already in the equipment.
4. Minimum dropping point (°C).
5. Minimum EP/AW performance — 4-ball weld point/LWI (ASTM D2596-20) and/or Timken OK Load (ASTM D2509-20ae1), plus 4-ball wear-scar maximum (ASTM D2266-23) if relevant.
6. Water-washout requirement if the environment is wet (ASTM D1264 method, maximum % at the relevant temperature).
7. Base-oil viscosity range needed (KV40 or KV100).
8. Operating temperature range, minimum and maximum (°C).
9. Packaging format requested (400 g cartridge / 18 kg pail / 50 kg drum / 180 kg drum).
10. MOQ per SKU.
11. Incoterms 2020 and FOB port of loading.
12. Documents required (COA per batch, SDS, COO, PSI certificate if applicable).
13. Lead time.
14. Payment terms.

Sourcing EP Grease Through Altonex Global

Altonex Global is a B2B discovery and RFQ marketplace for lubricants and fast-moving auto spare parts — it connects buyers with independent suppliers and is never itself the seller, manufacturer, or certifier of any listed product. Suppliers listed under EP Greases are independently responsible for their own specifications, EP/AW test data, stock, quotations, lead times, and after-sales support.

Using the checklist and RFQ field list above, buyers can submit a Request a Quote or Contact Supplier enquiry directly from the EP Greases category, specifying NLGI grade, thickener system, minimum EP/AW test values, packaging format, and destination country so suppliers can respond with an accurate, batch-specific TDS and COA. For more B2B sourcing guides on greases, lubricants, and export procurement, visit the Altonex Global Knowledge Hub.

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