u/Confident_Disk7031

I own a Westinghouse WPX4400 pressure washer. This unit uses a 4400 psi engine direct drive triplex pump. In the User Manual supplied with the unit, it states that after the first 20 hours of use, and then annually, the oil in the pump should be changed using only SAE 85W-90 oil. However supplied with the unit was an Operation and Parts Llist Manual for the engine direct drive Triplex high pressure pump. In this document is states that non-detergent SAE 10W/30 oil should be used. Does anyone have an opinion which oil I should be using? I called Westinghouse Tech Support, and they recommended I follow the information from the pump operation and parts list manual, and use SAE 10W/30 non-detergent oil.