My sister gave me a pressure washer yesterday . It had belonged to my brother in law . I changed the nasty engine oil and drained and refilled the pump oil . The sticker on the pump said that 30wt Non Detergent oil was an acceptable substitute for actual pump oil . I found some at Walmart for $4 qt versus $15 for the real stuff . It's not going to get a lot of use so I'm hoping it will last me a while . Anybody else use 30 wt oil in their pump ?