SAE 10w30 100% Synthetic oil.
Depends on the size engine the pressure washer uses. Just fill it up to the full mark on the dipstick. Use SAE 10w30 synthetic oil.
SAE 30 full synthetic in the engine.
You use whatever the manufacture of the pump recommends. Most use Non Detergent 30 weight oil.
Absolutely not. Use 10w30 high detergent oil just like you use in your lawn mower or vehicle.
No because the gas powered pressure washers do not take oil. They are 4 strokes. Gas only.
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.
For the engine, not the pump, 10W-30 is what Briggs puts in them, but SAE 30 is acceptable if your are not running the pressure washer in cold temperatures. I highly recommend you use synthetic oil in any air cooled engine.
Water.
Depends on the manufacture and the size of the pump. These pumps use a special oil so contact the manufacture for the exact amount and type oil.
Use exactly what the manufacture recommends. They are all different so you need to contact the manufacture of the pump. According to my Craftsmans manual for a 3000 psi under "changing pump oil", it says use only high quality SAE 30 weight oil and use no special additives.
Last resort, if the oil and tar won't come off with regular cleaning brush, you can use a pressure washer surface cleaner from bestcargurus along with your pressure washer, that will surely do the job.