Practical operator guide for Canadian winter conditions: hydraulic fluid selection, warm-up sequences, and what to do at -40°C when the machine has been sitting overnight.
Every hydraulic system has a minimum temperature below which it shouldn't be used under load. Most Canadian operators know this in a general sense — "warm the machine up before you work" — but the specifics matter. The difference between a proper cold-start procedure and a half-hearted warm-up can be the difference between a machine that works all winter without issue and one that blows seals, cavitates pumps, and racks up repair bills.
This guide covers the practical side: why cold hydraulic oil is dangerous, what fluid to use in Canadian conditions, and the actual warm-up sequence — by temperature range. It applies to skid steers and compact track loaders operating with any hydraulic attachment.
Hydraulic oil is a lubricant, a power transmission fluid, and a heat transfer medium all at once. When it's cold, all three of these functions are impaired.
Cold oil is thick oil. Hydraulic pumps are designed to operate within a specific viscosity range. Below that range, the pump can't move fluid fast enough to fill the inlet port on the suction side, which causes cavitation — the formation and collapse of vapor bubbles within the pump. Cavitation is mechanically destructive and the leading cause of hydraulic pump failure in cold-start conditions.
At -20°C, a standard AW46 hydraulic fluid has dramatically higher viscosity than at operating temperature. At -30°C and below, some conventional hydraulic fluids have thickened to the point where pump damage is likely on startup if the system is immediately loaded.
Rubber seals and hydraulic hoses become stiffer and more brittle at low temperatures. Seals that flex and seal normally at operating temperature can crack or lose sealing capacity when cold. Hose reinforcement braid becomes more rigid, making hoses more vulnerable to kinking damage. These issues are mostly mitigated by warming the system before putting it under load.
Water that has accumulated in the hydraulic reservoir from condensation will freeze at sub-zero temperatures. Ice in a hydraulic circuit can block filters, restrict ports, and cause catastrophic pump failures. This is a particular concern on machines that have been sitting for extended periods without running.
This is where many operators make their first mistake. Standard AW46 hydraulic oil — the most common fill in skid steers — is formulated for operating temperatures from approximately 0°C to 60°C at normal viscosity range. It can function below 0°C but requires more careful warm-up procedures as temperatures drop below -15°C.
The number after AW is a viscosity grade (ISO VG). Lower number = thinner oil = better cold-temperature flow. Higher number = thicker oil = better high-temperature stability.
Multi-viscosity hydraulic fluids (e.g., HV46, 5W-40 hydraulic oil) use viscosity index improvers to maintain a wider usable temperature range. They flow better at cold temperatures than monograde equivalents while still providing adequate viscosity at operating temperature. For operators who run their machines year-round in Canada, a multi-viscosity hydraulic fluid is worth considering — it reduces the risk of cold-start damage without requiring seasonal fluid changes.
Check your operator's manual first. Machine manufacturers specify approved fluid types and viscosity grades for their hydraulic systems. Some warranties are voided by using off-specification fluids. The OEM spec is the starting point — any advice in this guide is supplementary context, not a replacement for the manufacturer's guidance for your specific machine.
What "warm the machine up" actually means depends on how cold it is. Here are practical procedures by temperature range.
This is the everyday Canadian winter startup in most of the country through much of the season.
This is the range most Canadian Prairie, northern Ontario, Quebec, and northern BC operators regularly face in January and February.
At these temperatures — regularly reached in northern Alberta, Saskatchewan, the Northwest Territories, and Yukon — additional measures are needed. This is not the time to rush.
What happens if you skip the warm-up: The most common result of cold-starting under load is hydraulic pump cavitation damage. Pump repair or replacement is a significant cost. Seal failures from cold-start pressure spikes are also common — blown cylinder seals, hose failures, and valve damage can all result from immediate high-pressure demand on cold fluid.
These failures don't always happen the first time you short-cut the warm-up. They accumulate. Internal pump wear builds up over multiple cold-start incidents until a component fails. By then, the connection to the cold-start procedure has often been forgotten.
Before the first sustained cold snap of the season:
Even after proper warm-up, running hydraulic attachments at -30°C or colder requires some adjustments: