Magura USA Royal Blood Hydraulic Clutch Oil (4oz) Some say it has a secret power. Filling and bleeding of a Magura hydraulic clutch is not a routine chore and should only need to be done when air infiltration within the system is suspected. Magura uses mineral oil, which does not absorb moisture from the environment, to lubricate the whole system. The only time anyone should ever need to replace the hydraulic fluid in a Magura system is following a hydraulic line exchange, a system upgrade, a crash which has damaged the system components or in a situation where a lack of fluid within the system has If replacement of the system&#39;s fluid is absolutely required, use only MAGURA Royal Blood Mineral Oil and never DOT.