Hydraulics that hold their film hot and still flow cold
HVLP is the high viscosity index series. It is an HLP with a flatter viscosity–temperature curve — same anti-wear performance, far less change between a winter morning and a summer afternoon. Six grades, ISO VG 15 to 100.
What the viscosity index buys you
Viscosity index measures how much an oil thins as it warms. A higher number means a flatter curve. It is not a quality ranking — on a system that runs at one steady temperature all year it buys nothing. On a system that does not, it is the difference between holding a film and losing one.
The comparison below is between our own grades at the same nominal ISO VG. At 40 °C they are the same oil. At 100 °C they are not.
| ISO VG | Grade | KV 40°C cSt | KV 100°C cSt | VI | Pour °C |
|---|---|---|---|---|---|
| 32 | HLP 32 | 32.00 | 5.350 | 100 | -30 |
| HVLP 32 | 32.00 | 6.200 | 145 | -45 | |
| 46 | HLP 46 | 46.00 | 6.650 | 94 | -24 |
| HVLP 46 | 46.00 | 8.070 | 148 | -42 | |
| 68 | HLP 68 | 68.00 | 8.770 | 100 | -24 |
| HVLP 68 | 68.00 | 11.02 | 153 | -42 |
Read the VG 46 pair: identical at 40 °C, but at 100 °C the HVLP is roughly twenty percent thicker, and its pour point is eighteen degrees lower. One number is the margin between a film and metal contact on a hot afternoon; the other is whether the machine starts on a cold morning.
Cold start is the other half
Pour point across the HVLP range runs from −39 °C on the heaviest grade to −51 °C on VG 15. The mineral HLP equivalents sit between −18 °C and −30 °C.
That matters where a pump has to fill its inlet before the system has warmed up. Too thick on the suction side and the pump cavitates — noise, erosion and damage that happens in the first minutes of the day rather than under load.
Where HVLP belongs
- Deck machinery and cranes exposed to the weather, where ambient swings through the seasons.
- Steering gear and hatch covers on vessels trading between cold and tropical waters.
- Outdoor plant that starts cold and runs hot — the widest temperature range in a working day.
- Systems where the pump maker specifies a viscosity window an HLP cannot hold across the range.
Where a system lives indoors at a controlled temperature, HLP does the same job for less. Specifying HVLP there is not wrong, it is simply paying for a property the system never uses.
Typical properties
Values from the SINOVA Group technical data sheets, Form No. 002-EN, issued 5 January 2025. Typical properties are based on current production; variations may occur.
| Product | KV 100°CcSt | KV 40°CcSt | VI | Flash°C | Pour°C | Densityg/ml |
|---|---|---|---|---|---|---|
| HVLP 15 | 3.810 | 15.00 | 150 | 160 | -51 | 0.865 |
| HVLP 22 | 4.800 | 22.00 | 143 | 180 | -48 | 0.873 |
| HVLP 32 | 6.200 | 32.00 | 145 | 216 | -45 | 0.855 |
| HVLP 46 | 8.070 | 46.00 | 148 | 220 | -42 | 0.865 |
| HVLP 68 | 11.02 | 68.00 | 153 | 226 | -42 | 0.870 |
| HVLP 100 | 14.90 | on request | 155 | 230 | -39 | 0.880 |
The 40 °C viscosity for HVLP 100 is shown on request rather than printed. The data sheet we hold states a figure that is not consistent with an ISO VG 100 grade, and its own viscosity index and 100 °C value point elsewhere. We have asked SINOVA to confirm it rather than publish a number we cannot stand behind — the confirmed value is sent with any enquiry.
Questions we get asked
What do HLP and HVLP mean?
They are DIN 51524 hydraulic oil classes, and the letters are cumulative. HLP (Part 2) is a hydraulic oil with anti-wear, oxidation and corrosion protection. HVLP (Part 3) is an HLP with a high viscosity index — a flatter viscosity–temperature curve. It adds to the anti-wear performance rather than replacing it.
Choosing a hydraulic oil: ISO VG, HLP, HVLP and zinc-freeWhat is the difference between HVLP 46 and HLP 46?
At the ISO reference temperature of 40 °C they are the same oil: 46 mm²/s. The HVLP is roughly twenty percent thicker at 100 °C, which is the margin between holding a film and losing it on a hot afternoon, and its pour point is around eighteen degrees lower. Our HVLP 46 has a viscosity index of 148 and a pour point of −42 °C.
Two grades, both nominally ISO VG 46What is the difference between ISO VG 32, 46 and 68?
ISO 3448 defines a grade by its kinematic viscosity at 40 °C: an ISO VG 46 oil measures 46 mm²/s at 40 °C, within ten percent. That is a laboratory reference, not an operating condition. The pump cares about viscosity at the temperature the oil actually reaches in service, so the grade is chosen from the pump maker's operating window and the measured reservoir temperature under load.
Viscosity grade is set by the pump and the running temperatureWhen is an HVLP oil worth paying for?
When the system does not run at one steady temperature: deck machinery, outdoor plant, cold starts and hot afternoons in the same week. On a system that runs at the same temperature all year a high viscosity index buys nothing, and an HLP of the right grade does the job.
When a high viscosity index earns its costIs there an equivalent to another brand's HLP or HVLP 46?
We do not publish cross-reference tables. A hydraulic oil is matched on three things that are on every data sheet: the DIN 51524 class (HLP or HVLP), the ISO VG grade, and the viscosity at the temperature your pump runs at. Send us the data sheet of the oil in service and we will state which SINOVA Marine or Tomoil grade meets the same specification.
Send a data sheet for matchingWhat is a zinc-free hydraulic oil and when is it needed?
A hydraulic oil whose anti-wear chemistry is ashless rather than zinc-based. Some systems specify it because the pump or component maker excludes zinc additives. Alongside the SINOVA Marine HVLP range on this page, the Tomoil industrial range includes Zinc-Free HLP and Zinc-Free HVLP grades.
Industrial hydraulic grades