| abstract |
An ashless hydraulic fluid or paper machine oil having a VI between 155 and 300, a RPVOT greater than 680 minutes, and a kinematic viscosity at 40° C. from 19.8 cSt to 748 cSt. An ashless hydraulic fluid or paper machine oil having a high VI and high RPVOT comprising: a) a Group III base oil with a sequential number of carbon atoms, and defined cycloparaffin composition or low traction coefficient, b) an ashless antioxidant additive concentrate, and c) low amount of VI improver. A process for making an ashless hydraulic fluid or paper machine oil comprising a) hydroisomerization dewaxing, b) fractionating, c) selecting a fraction having a very high VI, and a high level of molecules with cycloparaffinic functionality or a low traction coefficient, and d) blending the fraction with an ashless antioxidant. Also, a method of improving the oxidation stability of an ashless hydraulic fluid or paper machine oil. |