Do all hydraulic systems use oil? Or do only some? Please give a list. Thanks.
a hydraulic system can use any fluid ... you need to worry about temperature raised within the fluid during operation, and how to dissipate. Also, large pressure changes could cause the fluid to evaporate
The term Hydraulic actually refers to water, and water systems, which have been around a lot longer than the day Jed Clampett of the Beverly Hillbillies discovered oil in his backyard shooting a rabbit. Which means that dams and ancient water wheels are hydraulic systems that do not use oil. Water could be used in modern hydraulic systems, but it would rust everything and not provide needed lubrication.
If it's hydraulic, it uses oil of some kind, usually, and not surprisingly: hydraulic fluid.
