I am interested in opinions on the best way to flush a hydrualic reservoir. The particular machine I am working on recommends using diesel fuel to flush the reservoir. I had someone ask if this is a proper technique and I didn't have a good answer for them. The machine uses 10W30 engine oil as the hydraulic fluid.

diesel fuel has the properties of being very thin (and easy to flush with) and evt. residues will mix with the oil. (Have in mind that evt. large ammounts of diesel in oil will decrease the flash point.)

If you are planning a high turbulence flushing you might be better of using a thin hydraulic oil (ISO VG 15, 22 or 32).