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Does your Hydraulic Oil Require a Change or Flush

NOTE: The advice provided in this article is not intended to supplement the services of a professional. The rigors of switching hydraulic oils may not be appropriate for the average hydraulic equipment user. Please seek the appropriate professional assistance when changing or flushing a hydraulic system.

Deciding whether to change your hydraulic oil or flush your hydraulic system is an important question because it involves not just the health of your machine but costs related to fluids, filters, downtime, and labour. Replacing hydraulic fluid means draining out the old fluid and adding fresh hydraulic fluid. On the other hand, flushing the entire system is more thorough and complicated - it not only gets rid of the old hydraulic fluid, but helps to flush out contaminants.

Your equipment’s user manual will provide the best guideline on when to change out your hydraulic fluid. Guidelines vary according to the manufacturer and type of machine, for example, experts recommend that you change the hydraulic fluid every 1,000 hours in most skid steer loaders. 

Another indication of when to change your hydraulic fluid would be determined by performing regular oil analysis. This allows you to ensure you only change out the hydraulic oil when it is really essential, so it isn’t done too soon or too late.

It is also important to note that hydraulic fluid degrades over time.  The hydraulic fluid degrades even faster if a machine has been running too hot or if the machine has been working in extreme or harsh environments. In these instances it’s probably best to change out the hydraulic fluid more often.

A machine that has been properly maintained and hasn’t experienced issues with major hydraulic failures or contamination should not need flushing. In such cases, a hydraulic fluid change should be sufficient.

In an ideal world, hydraulic fluid would only need to be replaced. However, there are situations in which the hydraulic system really needs to be flushed.

A hydraulic flush purges the entire hydraulic system of sludge, contaminants (including water, air, and particulate matter), and degraded hydraulic fluid.

The following are instances of when a flush may be necessary:

  • If the equipment is new, has been recently overhauled, or has not been used for some time
  • If the hydraulic system experiences a major failure, especially if a filter or contamination was involved
  • If the hydraulic fluid has degraded or formed sludge
  • If the machine is going to need a new type of hydraulic fluid

Why should you flush new equipment? Some experts recommend that you flush the system to rid it of any built-in contaminants. The same is true for equipment that has been recently overhauled and has new components in the hydraulic system.

You’ll also notice that flushes are recommended if the machine is going to have a new type of hydraulic fluid added. Always consult a professional if you are looking to switch brand and/or type of hydraulic oil as the additives may not be compatible with each other.

Just because the changeover has been completed does not mean that you are “out of the woods.” Your system will need to be closely monitored for a while to make certain that the flushing was thorough. Taking the time to verify that the system is fully flushed, and purged of the old fluid prior to introducing any new fluid, will go a long way toward ensuring a healthier hydraulic system.


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