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Hydraulic systems found on heavy machinery are under a lot of demand, even more so as manufacturers move to lighter and more efficient designs. Choosing the right hydraulic oil for your heavy equipment, whether you’re operating a single piece of machinery, running a farm or a fleet of construction equipment, is critical to keeping your business running.

As hydraulic systems have changed, operators expect even more out of them, but may spend less time on maintenance. What factors go into choosing hydraulic oil for your equipment? Basically, the name of the game is “high performance.” Here are a few things to keep in mind when selecting hydraulic oil.


Older hydraulic systems used heavier oils and larger reservoirs, while newer systems are moving in the opposite direction. Pumps are working proportionately harder with smaller gearboxes, and low-viscosity hydraulic oil flows better, removing contaminants more effectively while generating less heat. The lowest-viscosity oil specified by your equipment manufacturer will prevent excess stress and improve lubrication and protection.


Some hydraulic systems specify hydraulic fluid based on engine oils, while others call for anti-wear hydraulic fluid. Industrial hydraulic fluid doesn’t mix with engine oil or gear oil but instead is in a dedicated hydraulic system. Dedicated hydraulic oils are even available in environmentally friendly formulations.


Though new hydraulic oil may meet specifications put forth by the manufacturer, it may lose its effectiveness under the extreme demands of modern gearboxes and hydraulic systems. Look for oil that is formulated for your application and have it tested regularly. Maintain proper fluid level and replace hydraulic fluid when worn.


Demulsibility is the hydraulic oil’s ability to release water, but this decreases as water content increases. Engine-oil-based hydraulic fluids are more hygroscopic than anti-wear hydraulic fluids, so demulsibility drops faster. Water can get into the system in several ways, such as through worn seals, breather caps, condensation that arises during cool down and high-pressure washes. Hydraulic oil becomes more prone to foaming as water content increases. Water, of course, is useless as a lubricant, and foamed oil won’t drive hydraulics or protect moving parts. A lab test can reveal if your hydraulic oil is nearing its limits.

Choosing hydraulic oil, especially if you’re in charge of maintaining a fleet of vehicles and equipment, can’t be taken lightly. Companies haven’t come out with a single hydraulic fluid or oil that can meet the demands of every piece of equipment in your stead, whether it’s a skid-steer, a snowplow or an excavator. Mixing two types of oil can lead to premature wear. True, adding the “wrong” hydraulic fluid might get you out of a jam, but the system will need an immediate service to ensure it’s working properly.

Check out all the chemical products available on NAPA Online or trust one of our 16,000 NAPA AutoCare locations for routine maintenance and repairs. For more information on choosing hydraulic oil, chat with a knowledgeable expert at your local NAPA AUTO PARTS store.

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