Hey guys I just purchased a used Ridgid 3000 psi RD80746 pressure washer with the AR axial pump model RMV2.3G30. Im going to change the engine oil, sparkplug, and take the gas tank off and clean before I start using. I was going to change the pump oil but after alot of research online im pretty confused. On the pump case it says sae75w90 but online it says to use only AR64545 oil and nothing else will work. I know the plug for the oil is behind the manifold and it takes 2.2oz but my question is do I really need to change it? Is the oil supposed to be changed periodically or is it good for the life of the pump or until a repair is needed. The pump isn't leaking visibly from the outside but not sure if it's leaking internally because there isn't a sight glass. Any advice or recommendations is much appreciated. Thanks in advance.