What kind of oil do you use in a Campbell Hausfeld pressure washer pump?

These use a special oil that you must use based on the type of pump you have. If you have a cheap wobble pump, the kind mounted underneath the engine it uses SAE 20w for cold weather use or SAE 30W for warm weather use, Non-Detergnet oil. If you are the more expensive pump mounted behind the engine then it may use the same oil. Check with Campbell Hausfeld to be sure.