Truck and bus power steering uses whatever motor oil is used for the engine, usually 15W-40.
The edge cases are Honda/Acura and Euro cars calling for Pentosin CHF or Mercedes ZH-M fluid. PSF seems to be 30W base stock and a good dose of ZDDP or an organosulfur compound in it.
The edge cases are Honda/Acura and Euro cars calling for Pentosin CHF or Mercedes ZH-M fluid. PSF seems to be 30W base stock and a good dose of ZDDP or an organosulfur compound in it.