In a previous post, we looked at the reasons why a quality hydraulic oil should be used in your hydraulic system. We ascertained that an oil without a good enough base oil can result in all manner of issues. One of them being that oils such as motor oil have too many additives as they won’t easily let go of moisture in the oil. In this post, we’re going to look at the measurements that you need to take note of when looking for a good base hydraulic oil. First off, take a look at the Oxidation Stability Test results which may state something like ASTM D-943. This is a test procedure which provides some insight into the testing process that the hydraulic oil went through. The results are reported in hours of performance in resisting oxidation at elevated temperatures. For example, this might be 5000 hours. If it is 5000+ hours then you can rest assured that it has a high quality base oil. Most hydraulic oils will be displaying a report of between 1000 and 3000. If you don’t see oxidation stability on the sheet, then you’ll know that the performance wasn’t good enough to mention. Another report to look for is the hydraulic oil’s pour point. For example you may see -27F listed, which is an outstanding result for just one product. Those hydraulic oils that of a lesser quality won’t flow at 0 degrees. It’s not common that hydraulic systems that have to operate at temperatures as low as these, but it’s a factor that will provide you with an indication of the quality of your product. Another number to look for is the measure of the VI. If it’s 100 then it’s most likely a good oil. Synthetic oils may have a Viscosity Index of 120, with lesser oils in the 80 – 90 mark. At the end of the day, the quality of your hydraulic oil is vital to the good performance of your hydraulic system. Hopefully we have shed some light on what you need to consider when looking for a quality hydraulic oil for your system.