Which Hydraulic Oil for a Toronto Winter? HM 46, HV 32 or HV 46
Short answer: In the Toronto area, run an ISO 46 anti-wear hydraulic oil (HM 46) from April through November, and switch to a high-viscosity-index ISO 32 (HV 32) from December through March. If you would rather not change oil twice a year, HV 46 covers the full season range for most fleets, down to about −12 °C on a direct cold start.
Every February we get the same phone call. A machine that ran fine all summer is slow to respond on a cold morning, the pump whines for the first ten minutes, and by spring it needs a rebuild. Nine times out of ten the machine is still running summer oil.
This guide is written for excavators, wheel loaders, dozers, skid steers, cranes and other heavy equipment working outdoors in Toronto and the Greater Toronto Area. It applies to any brand — Caterpillar, Komatsu, John Deere, Hitachi, Volvo, SANY, XCMG, LiuGong — because the deciding factor is the temperature of the oil, not the badge on the machine.
Why cold oil damages hydraulic pumps
Hydraulic oil gets thicker as it gets colder, and the change is not gradual — it is exponential. An ISO 46 oil that measures 46 cSt at 40 °C can be over 3,000 cSt at −20 °C.
Most piston and vane pumps are specified for a maximum start-up viscosity somewhere between 1,000 and 1,600 cSt. Above that, the pump turns faster than the oil can flow into its inlet. The pressure at the inlet drops, vapour bubbles form in the oil, and those bubbles collapse violently against the metal in the high-pressure section. That is cavitation, and it pits the valve plate, the pistons and the housing a little more every cold morning.
The operator hears nothing unusual that day. The cost shows up one or two seasons later as a pump that should have lasted another five years.
Estimated viscosity at cold-start temperatures
| Oil | Viscosity index | Pour point | −10 °C | −20 °C | Direct cold start down to |
|---|---|---|---|---|---|
| HM 32 | 103 | −18 °C | ~800 cSt | below pour point | −12 °C |
| HM 46 | 101 | −15 °C | ~1,480 cSt | below pour point | −6 °C |
| AE 46 | 118 | −39 °C | ~1,240 cSt | ~3,500 cSt | −8 °C |
| HV 32 | 157 | −39 °C | ~510 cSt | ~1,190 cSt | −18 °C |
| HV 46 | 156 | −37 °C | ~830 cSt | ~2,010 cSt | −12 °C |
Viscosity index and pour point are published values from the Sinopec product data sheets. The low-temperature viscosities are estimates calculated with the ASTM D341 viscosity-temperature relationship from the 40 °C and 100 °C data, and the cold-start column assumes a 1,000 cSt limit. Your pump manufacturer's limit takes priority over this table.
April to November: run HM 46
Toronto's working season runs roughly −5 °C on an early April morning to +35 °C in a July heat wave. Under a full day of production, hydraulic oil in a hard-working machine sits somewhere around 70 to 80 °C, and most pumps want at least 10 cSt at operating temperature to keep a load-carrying film between the moving parts.
An ISO 46 oil holds about 11 cSt at 80 °C. An ISO 32 holds about 9 cSt, which is already below that line. That is why a 32 grade is the wrong choice for July, even though it starts more easily in April.
What to look for: an ISO 11158 L-HM or DIN 51524 Part 2 HLP anti-wear oil in grade 46, approved to Bosch Rexroth RDE 90235, Parker (Denison) HF-0 and Eaton (Vickers) requirements.
December to March: switch to HV 32
Toronto winters typically run between −25 °C in a cold snap and +5 °C on a mild afternoon, with January and February mornings often near −10 °C. A standard HM 46 is effectively unpumpable at those temperatures — at −20 °C it is below its own pour point.
HV 32 solves this from both ends. Its viscosity index of about 157 means it thins out far less as it heats up, so even though it is a lighter grade, it still measures around 10 cSt at 80 °C — essentially the same protection HM 46 gives in summer. At the cold end, it starts without a fight down to roughly −18 °C, and lower than that after a proper warm-up.
What to look for: an ISO 11158 L-HV or DIN 51524 Part 3 HVLP oil in grade 32. The letters that matter are HV, not HM.
When to switch: change to winter oil by late November and back to HM 46 in April. Drain and flush rather than topping up, so you are not carrying half a tank of summer oil into January.
One oil all year: HV 46
Swapping oil twice a year is not realistic for every fleet. For mixed fleets, rental yards and machines that work through the winter, HV 46 is the practical compromise.
At operating temperature it is slightly thicker than HM 46 — about 13 cSt at 80 °C — so nothing is given up in summer. On a cold start it manages about −12 °C directly, and colder with a warm-up cycle. Below about −20 °C, HV 32 remains the safer choice, because HV 46 is roughly 70 percent thicker at that temperature.
Where AE 46 and AE 5000 fit
Two Sinopec products sit above the standard lines and are worth knowing about.
SINOPEC AE Hydraulic Oil is a premium L-HM oil built on Group II base stocks, with a viscosity index of 118 and a pour point of −39 °C. In grade 46 it drops straight into an HM 46 application, starts more easily on frosty mornings, and carries JCMAS HK approval for Japanese equipment. It is a sensible upgrade for shops that want longer drain intervals without changing what the machine is specified for.
SINOPEC AE 5000 Multigrade Long Life is an L-HV oil with significantly extended service life, available in 32, 46 and 68. AE 5000 32 is a direct upgrade path from HV 32 for winter work, with a pour point of −45 °C and JCMAS HK approval. It suits operators who want to stretch oil change intervals while keeping cold-start performance.
Four things every operator should know
1. Warm up before you load. Below −10 °C, idle the machine 5 to 10 minutes, then cycle each function through its full stroke with no load before starting production. This pushes warm oil through the lines, cylinders and motors, not just the pump.
2. Check the plate on the hydraulic tank. Most machines carry a plate listing the oil grade for each ambient temperature range. It beats any general guide, including this one.
3. Don't judge an oil by its pour point alone. A low pour point means the oil still flows in the drum. It does not mean the pump can pull it in. Viscosity at start-up temperature is the number that matters.
4. Don't mix HM and HV long term. Topping up a winter fill with summer oil erodes exactly the cold-start margin you paid for.
Frequently asked questions
Can I use HV 32 all year in Toronto?
You can, and many light-duty machines do fine on it. The caution is heavy summer work: at 80 °C an ISO 32 oil runs near the lower viscosity limit of most pumps. For machines that dig hard through July and August, HV 46 is the better year-round choice.
What is the difference between HM and HV hydraulic oil?
HM is a standard anti-wear hydraulic oil with a viscosity index around 100. HV is a high-viscosity-index version, typically 150 or above, which means its viscosity changes much less with temperature. Both meet the same anti-wear requirements; HV adds cold-start capability and a wider working temperature range.
Is AW 46 the same as HM 46?
Broadly yes. "AW" (anti-wear) is a North American trade description, while HM is the ISO 11158 category designation. Most AW 46 oils meet ISO L-HM and DIN HLP requirements, so an AW 46 and an HM 46 are usually interchangeable — check the data sheet for the approvals your pump maker requires.
How cold is too cold to start a machine?
It depends on the oil in the tank, not the weather. As a rule of thumb, once the oil is thicker than about 1,000 cSt you are into warm-up territory, and past roughly 1,600 cSt you risk cavitation no matter how gently you start. For HM 46 that threshold arrives around −6 °C; for HV 32, around −18 °C.
Do I need to flush the system when switching oils?
For a seasonal HM-to-HV change, drain the tank and run the machine briefly to push old oil out of the cylinders and lines, then top up. A full flush is only necessary when switching between incompatible fluid types, such as moving from a mineral oil to a fire-resistant or biodegradable fluid.
Where can I buy Sinopec hydraulic oil in Ontario?
BuySinopec is the authorized Canadian distributor of Sinopec lubricants, shipping HM, HV, AE and AE 5000 hydraulic oils in 18 L pails, 200 L drums, 1,000 L IBC totes and bulk from the Greater Toronto Area.
Not sure what your fleet should be running?
Send a photo of the plate on your hydraulic tank, or tell us the machines you run and where they are parked overnight, and we will tell you exactly which grade to order and when to switch. Email kun@buysinopec.ca, or browse the hydraulic oil range.
All temperature ranges reflect Toronto-area climate averages. Viscosity figures are typical values from Sinopec product data sheets (July 2025) plus ASTM D341 estimates, and are intended for general guidance. Always follow your equipment manufacturer's recommendation.