Last year I notice my PW was struggling whenever I started it. It took about 5 min before it would start to run normal. I had never changed the pump oil, as some where in the manual it say do not change it. I was unsure of what to do, I decided to change the oil. It was grey in color suggesting water is in it, which is not good. It did smell like gear oil. The pump manual says only use this special AR64546 From AR North America. It is about $16 for not even 5 OZ. A sticker on the pump says to use 75w-90 oil, which is gear oil. No other info. Everything I have ever read about pump oil say to use non-detergent(ND). I think it has something to do with how ND oil handles water. Someone will correct me if this is not accurate. If you know, Please do chime in! I could not find any ND Gear oil. I was in Lowes and bought a bottle of "Pressure washer pump oil" branded Pro Select. No viscosity was on the bottle, at the time. I assumed it is ND. Feeling like It was low risk, I put it in. It only takes about 2 Oz. After that It ran great for all last season. This year it showed the same problem at start up. It must have a slow water leak into the pump oil chambe. I need to address that or keep changing the oil as the symptoms arise.
I noticed this year the Pro Select pump oil at Lowes is currently labeled 10w-30. But still no mention of ND or HD. If you are changing the pump oil every year, as I likely have to, You might as well use the SAE30 ND Super Tech. It is 1/6 the price and easily available. I still do not know of any gear oil that is ND. If you suspect water creeping into the pump oil, I woud assume the ND feature is more valuable than a slight viscosity change from spec. I do not like to assume and if someone knows for sure, I am open to hear what they care to share about this topic.
