ohh. didn't know that. I use hot water when its cold outside.

 

A properly set-up pressure washer that doesn't have too much pressure, and has a 35* degree or greater nozzle installed is perfectly fine. Obviously you don't want to use one that has too much pressure, or has too narrow of a nozzle that will strip your paint off.

If I'm preparing to do a clay application and apply paint sealant, I will start with a wide-angle nozzle, and set the pressure washer up to draw in warm soapy water for the pre-rinse, then I'll put a 35* nozzle on and finish rinsing it off with straight water, then soapy water with washmits, then rinse again, then dry.

Warm soapy water is fine if you're preparing to clay and strip off the old wax.

I actually used to clean off the entire exterior of my vehicle with a steam gun, damn it used to make the paint so clean in preparation for claying and applying sealant, and it was perfectly safe for the paint finish.

Most damage is caused to paint by burning it with a machine buffer, excessively buffing brand new paintjobs (that have soft clearcoats), burning paint with a heatgun when removing vinyl decals and emblems (you should use heavy-duty waxed cotton dental floss for removing emblems instead), and people who rub in products like Klasse Red Bottle and waxes with excessive pressure on the application, instead of just dabbing it on lightly, causing swirl marks everywhere...