Bearing grease viscosity vs NLGI consistency
NLGI grade and base-oil viscosity describe different properties.
On this page9 sections ⌄
What to check
Read two separate fields
NLGI describes grease consistency; base-oil viscosity describes resistance to flow at a stated temperature. NLGI 2 is not a universal viscosity recommendation.
Operating temperature matters
Compare viscosity at the expected operating temperature using the lubricant data and required bearing viscosity. An ISO VG number refers to viscosity at 40 °C, not every service temperature.
Build the evidence
Record base oil, thickener, NLGI, viscosity at stated temperatures, speed applicability and temperature limits. An absent field should remain unknown in your selection notes.
Direct answer
Read consistency and base-oil viscosity separately. NLGI is a grease consistency classification based on worked penetration; viscosity describes the base fluid at a stated temperature. Two NLGI 2 greases can have different base oils, viscosity, additives and intended duties.
NLGI consistency chart — worked penetration at 25 °C
| NLGI grade | Worked penetration (0.1 mm) |
|---|---|
| 000 | 445–475 |
| 00 | 400–430 |
| 0 | 355–385 |
| 1 | 310–340 |
| 2 | 265–295 |
| 3 | 220–250 |
| 4 | 175–205 |
| 5 | 130–160 |
| 6 | 85–115 |
The numerical grade increases as the grease becomes firmer; the penetration range decreases. These are classification ranges, not a viscosity chart or a bearing suitability ranking. A published intermediate consistency must be retained as stated, not rounded to a different grade.
Real grease records: compare fields rather than colours
Selected manufacturer technical values, not an interchange or approval list. Viscosity values are for the base oil, in mm²/s (cSt).
On a small screen, scroll the table sideways to read every column.
| Exact product | NLGI | Thickener | Base oil | Viscosity at 40 °C | Viscosity at 100 °C |
|---|---|---|---|---|---|
| SKF LGMT 2 | 2 | Lithium | Mineral | 110 | 11 |
| SKF LGHP 2 | 2–3 | Di-urea | Mineral | 96 | 10.5 |
| Mobil Polyrex EM | 2 | Polyurea | See exact product data sheet | 115 | 12.2 |
| Mobil Polyrex EM 103 | 3 | Polyurea | See exact product data sheet | 115 | 12.2 |
Polyrex EM and EM 103 have the same listed base-oil viscosities but different consistency grades. LGMT 2 and Polyrex EM share a grade but not the same listed formulation or viscosity. Neither comparison proves that the products can be mixed.
SKF suffixes such as LGMT 2/1 and LGMT 2/5 identify pack sizes for LGMT 2; they do not change its NLGI grade to 1 or 5. Retain the exact product label and current regional data sheet. This reference does not reproduce safety data sheets or claim a lubricant has an unlisted equipment approval.
Which property answers your question?
On a small screen, scroll the table sideways to read every column.
| Question | Use this field | Do not substitute |
|---|---|---|
| How firm is the grease? | NLGI / worked penetration | Base-oil viscosity |
| How viscous is the lubricating fluid? | Base-oil viscosity at stated temperature | Colour or NLGI |
| Can the grease flow through my lines? | System-approved pumpability at actual temperature | A consistency grade alone |
| Can I mix old and new fill? | Evidence for the exact two products | Same colour or brand |
Reference scope
Manufacturer and technical-institute records reviewed for this page: NLGI consistency glossary; NLGI technical FAQs; SKF LGMT 2 technical product record; SKF LGHP 2 technical product record; Mobil Polyrex EM / EM 103 product data; retrieved 2026-10-01 UTC. Values are a dated reference snapshot, not an OEM approval or a substitute for the current technical and safety documents. Original source addresses and retrieval evidence are retained in the private content audit.
Continue with real catalogue data
Preserve the full model, source description and unknown fields when making your shortlist. This reference website does not sell bearings or certify a replacement.
Related questions and tools
Grease vs oil bearing lubrication
Choose the lubrication system before choosing a product name.
Read and apply →Bearing grease compatibility: mixing & changeover
Grease colour does not identify its chemistry or establish compatibility.
Read and apply →Lithium, polyurea & moly bearing greases
A thickener or additive name alone does not define an approved bearing lubricant.
Read and apply →Bearing regreasing quantity & interval
A useful maintenance schedule needs the actual equipment duty, not a universal number of pumps or months.
Read and apply →Sealed-for-life bearings: lubrication & maintenance
Sealed-for-life describes a maintenance concept, not infinite bearing or grease life.
Read and apply →High-temperature bearing lubrication checklist
Check the whole bearing system at temperature: lubricant, seals, cage, clearance and material stability.
Read and apply →Low-temperature bearing grease & starting torque
A bearing that runs acceptably when warm may struggle at a cold start.
Read and apply →High-speed bearing grease, oil-air & oil-mist checks
High-speed selection combines bearing geometry, lubricant supply, heat and preload.
Read and apply →Water exposure & food-grade bearing lubrication
A food-contact category and water resistance answer different questions.
Read and apply →Cleaning bearings before relubrication
Cleaning is a controlled maintenance operation, not a cure for damaged raceways.
Read and apply →Plain, linear & solid-lubricated bearing maintenance
Not every component in a bearing catalogue follows a rolling-bearing greasing procedure.
Read and apply →Wheel-bearing grease: NLGI ratings, types & product comparison
Choose wheel-bearing grease from the hub specification and service conditions, not its colour or the word 'premium'. Compare documented automotive and marine examples, then check the exact assembly before use.
Read and apply →Reference basis & data limits
Manufacturer terminology is retained in the product records. Technical reference basis: JTEKT Basic Bearing Knowledge (boundary dimensions, tolerance classes and lubrication); NSK Bearing ABCs (lubrication, designations and clearance); NTN technical FAQs (closure codes and component interchange); SKF rolling-bearing selection and maintenance references.
Selection workflows and catalogue grouping are BearingScope editorial aids. Verify the current drawing and application requirements before using a candidate. Missing database information is not converted into an assumed match.