Changing your hydraulic oil is not quite as simple as it looks. You need to take more into account than might first seem apparent. When you decide to change your hydraulic oil, you need to know that although you will have attempted to drain all of it, it won’t all have left the system. It’s for this reason that you need to ensure that your previous oil is going to be compatible with the new one. Here at Hydraproducts, we use a number of different oils when we test both our bespoke and non-bespoke mobile hydraulic systems. We follow the process below to ensure that it’s changed under controlled conditions: Drain the hydraulic fluid from the tank Refill the tank with the new oil Switch on the machine to work for between 10 and 15 mins Turn the machine off Drain the hydraulic fluid from the tank Refill the tank with the new oil Get the machine working for between 10 and 15 mins Turn the machine off This process, although sometimes run through up to 4 times, will eventually whittle down the previous oil so that there is eventually more than 95% of new oil in the system. Note : 1. You’re going to get through a lot of oil 2. If there is a 95/5 mix ratio of the old and new oil, they will still need to be compatible If you don’t want to get through all that oil, you could try mixing your oils beforehand using a 75/25 mix and give it a good shake, wait and observe or even put the blend in a temperature controlled zone for one month. The temperature should of course be in line with your operating temperature/climate so that you can see what might happen. You could then examine the blend to look for incompatibilities. However, if you go ahead and opt not to do this test, you could regret it when your machine suffers as a result. Compatible hydraulic oils are key to the performance and reliability of your system.