What this product reference covers.
Axle oil is a gear lubricant selected for hypoid, spiral-bevel or final-drive duty under a defined viscosity and performance category.
Products within the family.
Names used in commerce can overlap. Use the nominated standard and exact grade rather than relying on a generic product label.
Hypoid gear oil
Hypoid gear oil is a recognised axle oil category whose exact composition, grade limits and suitability must be confirmed from the governing specification and equipment requirement.
Limited-slip axle oil
Limited-slip axle oil is a recognised axle oil category whose exact composition, grade limits and suitability must be confirmed from the governing specification and equipment requirement rather than inferred from the generic label.
Final-drive oil
Final-drive oil is a recognised axle oil category whose exact composition, grade limits and suitability must be confirmed from the governing specification and equipment requirement rather than inferred from the generic label.
Synthetic axle lubricant
Synthetic axle lubricant is a recognised axle oil category whose exact composition, grade limits and suitability must be confirmed from the governing specification and equipment requirement rather than inferred from the generic label.
What the product is built from.
| Component | Technical role |
|---|---|
| Mineral, synthetic or renewable base fluid | Provides the principal lubricating film and viscosity-temperature foundation. |
| Anti-wear / extreme-pressure system | Protects loaded contacts where the application requires it. |
| Antioxidant and corrosion inhibitors | Control ageing, deposits and surface corrosion. |
| Application-specific additives | Tune detergency, friction, demulsibility, air release, tackiness or seal compatibility. |
Define the decision before selecting the panel.
- 01
Confirm new axle oil identity, grade and fitness for the intended application.
- 02
Detect contamination, degradation, mixing or storage-related change.
- 03
Investigate abnormal equipment, combustion, filtration or handling behaviour.
- 04
Establish a representative baseline for later comparison.
- 05
Support specification, maintenance and root-cause decisions with corroborated evidence.
What each result contributes.
“High” and “low” are directional investigation prompts, not pass/fail decisions. Corroborate them using the correct specification, baseline and companion evidence.
Open ASTM, ISO, IS/BIS, DIN and companion methods →| Test / parameter | Typical methods | Why it matters | Possible causes when high | Possible causes when low |
|---|---|---|---|---|
| Kinematic viscosity | ASTM D445 / ISO 3104 | Confirms grade and detects dilution, shear, oxidation or mixing. | Oxidation, wrong oil, soot, evaporation or heavy contamination. | Shear, fuel/solvent dilution, wrong grade or lighter make-up oil. |
| Acid number | ASTM D664 | Trends acidic constituents, oxidation and contamination against a new-oil baseline. | Oxidation, overheating, acidic contamination or wrong fluid. | Fresh oil, make-up dilution or formulation difference. |
| Water | ASTM D6304 | Quantifies moisture relevant to corrosion, additive loss and film strength. | Condensation, cooler/seal leak, washdown, storage or sampling contamination. | Dry operation or dehydration; hot sampling can reduce free-water representation. |
| Elemental analysis | ASTM D5185 with PQ / ferrography where needed | Screens wear, contaminants and additive chemistry within method limitations. | Wear, corrosion, dirt, additive source, wrong oil or maintenance debris. | Stable wear, dilution, filtration or particles too large for ICP response. |
| FTIR condition | ASTM E2412 trending | Tracks oxidation and selected molecular contaminants against a comparable reference. | Heat, extended service, contamination or depleted antioxidant reserve. | Fresh oil, make-up dilution or a non-comparable baseline. |
| Friction performance | OEM-approved bench, clutch, synchroniser or wet-brake test; product specification | Confirms the controlled friction response required by transmissions, wet brakes, limited-slip axles and shared-sump equipment. | No universal high direction: excess static friction can cause chatter or harsh engagement depending on the test. | Insufficient dynamic friction can cause slip, heat and clutch wear; interpret only against the approved fluid specification. |
| Ferrous debris / PQ index | Direct-reading ferrous density / PQ method; laboratory procedure | Responds to ferromagnetic debris including particles larger than routine ICP can efficiently detect. | Active gear, bearing, liner or steel-component wear; corrosion scale or maintenance debris. | Stable wear or little ferrous debris; a low value does not exclude non-ferrous or very fine wear. |
| Analytical ferrography / wear-particle morphology | ASTM D7690 or documented microscopic procedure | Examines particle size, shape, colour and concentration to distinguish rubbing, cutting, fatigue, corrosion and contaminant debris. | More severe particles, increasing concentration or a morphology consistent with active distress. | Few captured particles; poor agitation, settling or sampling away from the wear path can reduce recovery. |
| Wear / load-carrying performance | ASTM D4172; ASTM D2783 or application-specific gear/EP test | Characterises anti-wear or extreme-pressure performance for product qualification and comparative investigation. | For scar diameter: poor anti-wear response, contamination or depleted/additive-incompatible oil. | For scar diameter: stronger film/additive response; results do not directly predict a specific machine's wear rate. |
| Copper corrosion | ASTM D130; ISO 2160 | Screens corrosivity toward copper-containing bearings, coolers, bushings and yellow-metal components. | Reactive sulfur, acidic degradation, contamination or formulation incompatibility; report uses a corrosion rating rather than concentration. | A low corrosion rating is favourable but does not rule out in-service copper wear. |
Five-step evidence analysis.
Move from a trustworthy sample to a tested failure hypothesis, proportionate maintenance response and documented confirmation. Each step increases or reduces diagnostic confidence.
Choose a representative sampling procedure →- 01Validate the evidence: confirm asset identity, a repeatable live-zone sampling point, operating state, oil hours, make-up volume and recent maintenance for road-vehicle differentials. Repeat the sample when identity, container, flushing or handling is doubtful.
- 02Establish the correct baseline: confirm the declared axle oil grade, base chemistry and additive profile. Compare method-consistent results with new oil, the previous stable sample and rate of change rather than a universal limit.
- 03Build the contamination pattern: Check water, dirt and mixed lubricant evidence against seals, breathers, hub work and immersion exposure. Require an independent companion signal, inspection finding or filter observation before assigning a source.
- 04Test and localise the failure hypothesis: Correlate ferrous debris, copper, PQ and morphology with hypoid gears, bearings and final-drive duty. Check whether the proposed mechanism explains the full pattern, including contradictory or absent evidence.
- 05Select and verify proportionate action: Inspect the credible gear or bearing source, correct ingress or loading and verify the post-action trend. Record the intervention, resample at a risk-based interval from the same point and confirm that the trend responded as expected.