46 CFR §58.30-10

1. (a)The requirements of this section are applicable to all fluid power transmission and control systems installed on vessels subject to inspection.
2. (b)The fluid used in hydraulic power transmission systems must have a flashpoint of not less than 200 °F for pressures below 150 psig and 315 °F for pressures 150 psig and above, as determined by ASTM D92 (incorporated by reference, see § 58.03-1), Cleveland “Open Cup” test method.
3. (c)The chemical and physical properties of the hydraulic fluid must be suitable for use with any materials in the system or components thereof.
4. (d)The hydraulic fluid must be suitable for operation of the hydraulic system through the entire temperature range to which it may be subjected in service.
5. (e)The recommendations of the system component manufacturers must be considered in the selection and use of hydraulic fluid.