Hydraulic oil labels look like a code: HL 32, HLP 46, HM 68, HVLP 46, HLPD 46. The letters are not marketing. They come from two standards, and they tell you which additives the oil contains. Choosing the wrong type can mean worn pumps, sticky valves or oil that will not let water settle out.
HLP (DIN 51524-2) and HM (ISO 6743-4) both mean an anti-wear hydraulic oil, and they suit most industrial machines. HL is a basic oil without anti-wear additives, for low-pressure systems. HVLP (or HV) adds a high viscosity index for machines that see wide temperature swings. HLPD contains detergents and is meant only for specific machine tools.
Most labels in India follow one of two systems:
The two systems line up closely:
| DIN 51524 | ISO 6743-4 | What is inside | Typical use |
|---|---|---|---|
| HL (Part 1) | HL | Rust and oxidation inhibitors | Low-pressure systems, no anti-wear needed |
| HLP (Part 2) | HM | HL + anti-wear additives | Most industrial hydraulics with vane, gear or piston pumps |
| HVLP (Part 3) | HV | HM + viscosity index improver | Outdoor and mobile machines, wide temperature range |
| HLPD | (no exact match) | HLP + detergent/dispersant | Machine tools where small amounts of water and dirt must stay suspended |
| HLP-type with anti-stick-slip | HG | HM + friction modifiers | Machines that use one oil for hydraulics and slideways |
The number after the letters is the viscosity grade. HLP 46 means an anti-wear oil of ISO VG 46. If you are unsure about the number, start with our guide to hydraulic oil 32 vs 46 vs 68.
HL oils protect against rust and oxidation but carry no anti-wear additives. They suit low-pressure circuits, some older machines and a few lubrication systems. Running a modern high-pressure vane or piston pump on HL oil can wear the pump quickly. Use it only where the manual asks for it.
Anti-wear additives form a protective film on metal surfaces when the oil film gets thin, for example at the vane tips of a pump under high pressure. That is why HLP (or HM) is the standard choice for presses, injection moulding machines, machine tools and most plant hydraulics.
Within HLP oils there are two families:
Mixing the two families can, in some cases, form deposits that block fine filters and servo valves. When switching type, drain and flush.
Viscosity drops as oil heats. An HVLP oil has a higher viscosity index, so it thins out less in the afternoon heat and thickens less on a cold morning. It makes sense for:
The trade-off is cost, and the viscosity improver can shear down over time in very high-pressure pumps. Choose a shear-stable grade for those.
HLPD oils carry detergent-dispersant additives. They hold small amounts of water and fine dirt in suspension instead of letting them settle. That suits certain machine tools where coolant splashes into the hydraulic tank, but it is wrong for systems where you want water to separate and be drained, such as large presses or turbines. Use HLPD only when the maker specifies it.
Where a hydraulic leak could reach a flame, molten metal or a hot surface (die casting, steel plants, furnaces), mineral oil can be a fire risk. ISO 6743-4 lists fire-resistant fluids: HFA and HFB (water-based emulsions), HFC (water-glycol) and HFD (synthetic, water-free). Changing over to these fluids needs care: seals, paints and filters must be compatible, and the system must be flushed.
Is HLP the same as HM hydraulic oil?In practice, yes. HLP is the DIN 51524-2 name and HM is the ISO 6743-4 name for an anti-wear hydraulic oil. Check the data sheet for the exact specification met.
What does AW hydraulic oil mean?AW means anti-wear. An "AW 46" oil is an anti-wear oil of ISO VG 46, which is broadly the same family as HLP 46 or HM 46.
Can I use HVLP instead of HLP?Usually yes, if the viscosity grade is right; HVLP simply handles temperature swings better. Using HLP where HVLP is specified is riskier, especially for outdoor machines.
What does the D in HLPD mean?Detergent/dispersant. These additives keep water and fine dirt suspended in the oil. Use HLPD only where the machine maker asks for it.
Share the oil type and grade written in your machine manual, or the pump make and model, and our team will tell you which Banesto hydraulic oil matches it.