The old style “wobble“ pump on my old Excell 2600 psi with the 5 hp Honda GC160 is getting tired. Pressure seems to have dropped the last couple of times I’ve used it. I checked the nozzles, water inlet and outlet, wand etc plus It’s also 15 years old so I bought a new axial pump off of Amazon and it’s much more powerful now. It has a sight glass and oil drain and The owners manual of this particular pump says to use 85w90 gear oil in the pump. Several pump manufacturers, Simpson, Cat, say to use 30 wt non detergent oil in their pumps which I’m inclined to use. I’m assuming my pump has 85w90 as the FF and am wondering if anyone else has used gear oil in their pressure washer pumps.