What this product reference covers.
Hydraulic oil transmits power while lubricating pumps, valves and actuators, carrying heat and contaminants, protecting against corrosion and releasing entrained air and water.
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.
HH / HL
Mineral-oil categories ranging from base fluids to products with oxidation and corrosion inhibition.
HM / anti-wear
Mineral hydraulic fluids with anti-wear performance, commonly zinc-containing or ashless.
HV / high viscosity index
Fluids formulated for wider operating-temperature ranges.
Fire-resistant and biodegradable fluids
Water-containing, water-glycol, phosphate-ester, synthetic-ester or other specialist fluids requiring method and compatibility control.
What the product is built from.
| Component | Technical role |
|---|---|
| Mineral or synthetic base fluid | Provides viscosity, lubricity, thermal behaviour and seal compatibility. |
| Anti-wear system | Protects pumps and loaded surfaces; chemistry may be zinc-containing or ashless. |
| Antioxidant / rust inhibitor | Controls oxidation, sludge, varnish and corrosion. |
| Viscosity modifier | Supports viscosity retention across a wider temperature range in HV fluids. |
| Demulsifier and antifoam | Promotes water separation and controls foam without preventing normal air release. |
Define the decision before selecting the panel.
- 01
Confirm new-fluid category, viscosity grade and additive chemistry.
- 02
Control solid-particle cleanliness against component sensitivity and an agreed target.
- 03
Detect water ingress, oxidation, varnish precursors and cross-contamination.
- 04
Trend pump or valve wear using complementary elemental and particle methods.
- 05
Verify filtration and contamination-control effectiveness after maintenance.
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 |
|---|---|---|---|---|
| Particle count / ISO code | ISO 11500 / ASTM D7647; report ISO 4406 code | Quantifies cleanliness at defined particle-size thresholds. | Ingress, wear, maintenance debris, filter bypass/failure or poor sampling. | Effective filtration and exclusion; settling or an unrepresentative sample can under-report. |
| Kinematic viscosity | ASTM D445 / ISO 3104 | Confirms grade and detects oxidation, shear or mixing. | Oxidation, wrong oil, heavy contamination or evaporation. | Shear, wrong grade, solvent/fuel contamination or lighter make-up. |
| Water | ASTM D6304 | Quantifies water relevant to corrosion, additive loss and film strength. | Cooler leak, condensation, washdown, reservoir breathing or poor storage. | Dry operation or dehydration; method/sample handling still matters. |
| Acid number | ASTM D664 | Trends oxidation and acidic contamination relative to new oil. | Oxidation, overheating, wrong fluid or contamination. | Fresh oil, make-up dilution or formulation difference. |
| Elemental wear / additive profile | ASTM D5185 | Screens wear, dirt and cross-contamination within ICP particle-size response. | Pump/valve wear, corrosion, dirt or wrong oil. | Stable condition, dilution or large particles not represented by ICP. |
| PQ / ferrous debris | Particle quantifier and ferrography | Adds sensitivity to larger ferromagnetic wear debris. | Active severe wear, maintenance debris or magnetic contamination. | Low ferrous debris; non-ferrous wear still requires other evidence. |
| FTIR oxidation / contamination | ASTM E2412 trending | Tracks molecular change and selected contaminants against a baseline. | Thermal stress, oxidation, wrong fluid or contamination. | Fresh oil or make-up dilution; baseline mismatch can distort interpretation. |
| Air release / foam tendency | ASTM D3427 / ASTM D892 where applicable | Supports troubleshooting of compressibility, cavitation and reservoir foam. | Contamination, additive imbalance, wrong oil, suction leaks or poor reservoir design. | Favourable release/foam response under the method; field aeration may still be mechanical. |
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 mobile hydraulics. Repeat the sample when identity, container, flushing or handling is doubtful.
- 02Establish the correct baseline: confirm the declared hydraulic 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: Combine particle count, water, silicon and filter evidence to separate ingression, maintenance debris and internally generated particles. Require an independent companion signal, inspection finding or filter observation before assigning a source.
- 04Test and localise the failure hypothesis: Compare ICP metals with PQ, microscopy, pressure instability and pump or valve symptoms to localise wear. Check whether the proposed mechanism explains the full pattern, including contradictory or absent evidence.
- 05Select and verify proportionate action: Restore exclusion and filtration, correct the ingress source, inspect the implicated component and verify cleanliness from the same live-zone point. Record the intervention, resample at a risk-based interval from the same point and confirm that the trend responded as expected.