I've been running Honda Powered pressure washers with Cat pumps for well over 30 years with 30 grade non-detergent oil in the pumps. I have a machine here close to 30 years old that just started leaking a bit of water in the pump causing it to mix with the oil. Not bad considering the age. I also acquired one that needs a pump, it sat out over several winters and the water froze in the pump and ruined it, but that's a another story.