Avoiding Oil Degradation in Hydraulic Systems

Discover the top 5 causes of oil degradation in hydraulic systems and how to avoid them

Avoiding Oil Degradation in Hydraulic SystemsBased on the type of hydraulic equipment issues we see here at Bernell Hydraulics, we can safely say that oil contamination is a leading cause behind a majority of hydraulic system failures. This observation is backed up by scientific research—one study found that particulate-contaminated hydraulic oil was the cause of 82 percent of all hydraulic component wear while another found that 90 percent of all hydraulic system failures can be attributed to problems stemming from contaminated oil. We tell all of our clients to watch out for these top 5 causes of oil degradation & contamination to protect their hydraulic systems.

Water Infiltration

Water contamination typically arises from the condensation of hot, humid air inside the system, but it can also come from leaky parts or be introduced during a careless fluid change. Experts have found that when oil contains as little as 0.1 percent water by volume, bearing life will be cut in half and hydraulic pump performance will begin to suffer as well. In order to prevent water contamination from harming your equipment, you should take care to inspect seals regularly, get your fluids analyzed, and use high-performance fluids with demulsifiers that help separate water from oil for draining.


Overheating causes varnish formation in oil, which lowers the lubricating power of the oil and increases its viscosity. Exceeding recommended operating temperatures also causes oil additives to deteriorate more rapidly than they should. Bottom line, the hotter the oil gets, the less effective it will be in preventing friction within the system. If your hydraulic equipment is experiencing overheating issues, you will need to replace your oil twice as often for every 18 degrees above 130F.


Cavitation is basically the formation of air bubbles in your fluid. This is a huge problem because these air bubbles will collapse or implode when passing between differently pressurized parts of your hydraulic system. The resulting shockwaves can reduce the efficiency of your hydraulic pump, open clearances, and cause metal shavings or slivers to be dislodged from pump housing walls. Cavitation can be prevented by eliminating flow obstructions, undersized hoses, clogged breather caps, and pump over-speed issues.


When incompatible oils are mixed, byproducts like foam or sludge may be formed. These byproducts will gunk up your hydraulic system, potentially making water infiltration and cavitation problems worse and contributing to excess wear and tear on your system. In order to prevent the formation of byproducts, pick a fluid and stick with it. If you must change, be sure the system has been thoroughly flushed before introducing a new fluid.


Particulates are perhaps the most destructive type of hydraulic fluid contamination. Particulates may consist of metal slivers produced by cavitation issues or bits of dirt introduced into the system during maintenance. Either way, the particles can mix with oil or sludge to make valves stick or to score and gouge pump housings, wear plates, cylinder walls, etc. You can keep particulates from prematurely degrading your oil and causing parts failures through filtration. Be sure your filter capacity is at least twice the system flow rate for maximum protection, and check, clean, and replace the filters often.

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