Review on hydraulic fluids

The following information was published on the 2CV mail-list on the 7th of february 1997 by Adam Reif

"red" fluid is VEGETABLE base oil used in early hydraulic systems and is a Citroen term (red), but the fluids themselves are essentially clear like:

"green" fluid is a MINERAL base oil (MIL-H-5606) used in late hydraulic systems:

I just did a looksy on Univis J-13 and came upon and it talks about a Shell product called TELLUS T which is available in ISO grades 15, 22 and 32. It's supposed to be better than standard ISO 15 fluids. You'll have to decide for yourself.

Emergency LHM subsitutes:
Dextron Automatic Transmission Fluid (ATF) Type A (NOT TYPE F!!!) or 10W non-detergent oil (5W would be even better as it's much closer to the ISO 15 number, but I doubt you could find it.

Dextron is approximately 3 times THICKER than LHM. If you have an LHM system that is worn and causing a lot of pressure bypass, I suppose you could put Dextron Type A in there, and get a little more life ou of your worn out hydraulic system.

Four your information:

ISO VG Viscosity measurement in centistokes (cSt) at 40 C
AGMA American Gear Manufactures Association
SAE Society of Automotive Engineers e.g. SAE30
Saybolt These units of S.U.S. were used by various refiners to specify viscosity at 100 F or 210 F

If you want to have a handy reference chart of ISO/SAE crankcase oil/SAE gear oil viscosity equivalence check out which is from a Canadian Conoco (Noco) Oil web-site.

Last updated on: 23.01.1998, by Jint Nijman