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Views: 0 Author: Site Editor Publish Time: 2025-05-14 Origin: Site
In a hydraulic system, hydraulic oil is the lifeblood, and the hydraulic motor is the heart. Selecting the wrong fluid—often due to misunderstanding codes like HL, HM, HG, HV, and HS—can lead to premature wear, system failure, and costly downtime.
This comprehensive guide decodes these industry-standard oil codes based on ISO and GB/T 11118.1-2011, helping you make informed decisions that improve system longevity and performance.
Each oil grade serves a specific function and is formulated to meet distinct equipment requirements.
Standard: ISO-L-HL
Features: Base oil + anti-rust & antioxidant additives
Use Case: Low-pressure systems (<7 MPa), older piston pumps
Standard: ISO-L-HM
Features: HL base + zinc or ashless anti-wear additives
Use Case: Construction equipment, excavators, high-pressure hydraulic motors
Standard: ISO-L-HG
Features: HM base + stick-slip modifier
Use Case: CNC machines with combined hydraulic and guideway lubrication
Standard: ISO-L-HV
Features: VI > 130, excellent flow at low temperatures
Use Case: Cold climate machinery, outdoor mobile hydraulics
Standard: ISO-L-HS
Features: Synthetic base, pour point below -40°C
Use Case: Arctic operations, polar research stations, high-altitude machinery
A mining client used HL oil in a piston motor designed for high-pressure use. Within a month, performance deteriorated due to poor anti-wear capacity. Replacing the motor and switching to HM oil resolved the issue—but the lost time cost over $80,000.
In sub-zero conditions, standard HM oil thickened and caused the hydraulic motor to stall. Switching to HV or HS ensured reliable low-temperature starts and stable torque delivery.
Seawater intrusion in marine applications caused emulsification, leading to corrosion and motor failure. HS synthetic oil with better demulsification and rust protection resolved the issue.
| Equipment Type | Recommended Oil | Key Performance Parameter | Notes |
|---|---|---|---|
| Piston Motors (High-Pressure) | HM / HS | FZG ≥ 10 (anti-wear rating) | Do not mix brands |
| High-Speed Vane Motors | HV | VI > 150 | Regularly monitor viscosity |
| Excavator Main Pumps | HM | NAS cleanliness ≤ 8 | Maintain filtration systems |
| CNC Machines | HG | Static friction < 0.08 | Keep system free from contaminants |
| Arctic/Alpine Equipment | HS | Pour point < -40°C | Store in dry, cold-protected areas |
Q: Should I replace hydraulic oil if it turns dark?
A: Not necessarily. Perform lab tests for acid value, water content, and particulate levels.
Q: Can I mix hydraulic oils from different brands?
A: No. Different additive systems may cause chemical reactions. Always flush the system before changing oil types.
Q: Is hydraulic motor noise related to oil quality?
A: Yes. Oxidized oil leads to sludge formation and impaired lubrication, causing vibration and noise.
Q: How do I know when oil needs to be changed?
A: Regular testing for viscosity, oxidation, water content, and particle count is essential.
Q: What are the storage guidelines for hydraulic oil?
A: Store in sealed containers, away from heat and humidity, and avoid contamination.
Correctly identifying and applying hydraulic oil types—HL, HM, HG, HV, HS—is essential for protecting your hydraulic motor, especially under extreme pressure or environmental conditions. From factory floors to remote cold-weather sites, the right fluid keeps your system efficient, safe, and long-lasting.
