Diff clean is a silicone based cleaner that works by diluting the diff oil that it is to be removed from the differential. Since it is silicone based it will not contaminate the differential with other chemicals that may harm the seals or contaminate the new diff oil. 4oz. Instructions: 1-Open the differential, removed as much oil as possible but leave all the gears inside. 2-Pour Diff Clean in the differential and temporarily close the differential. 3-Agitate the oil by spinning the gears in the differential several seconds to dilute the diff oil. 4-Open the differential, pour out the diluted oil, a microfiber towel may be used to clean the differential. 5-Repeat steps 2 thru 4 approximately 3 times as required to completely dilute and clean the differential and gears. May require additional times if the oil is of very heavy viscosity. If available compressed air works well by blowing air into the differential with all the gears inside. Exercise caution when using this method, point away from you and/or cover with a cloth. Lastly remove all the gears from the differential and do a final wipe down. The result is a differential assembly that is completely clean without the use of any hard solvents. Using Diff Clean allows for a consistent operation of the differential and diff oil, changes in viscosity are consistent and accurate because differential will not have any residues of old oil.