Never use 0 on paint. 25 and up is usually safe for paint. I use 0 and 15 for hard to clean areas like wheel wells, undercarriage or inside of my wheels.

 

I don't consider a pressure washer particularity safe for any of my cars especially after taking some of the front bumper cover paint (or clear coat) off trying to get bugs off. I'd stick to the 40° setting and a long distance from the car until you know how your washer works. I've not found a good car wash soap for mine so have now restricted it to the wheels and underbody.

The numbers are the spray spread. Wider spread is less pressure but overall pressure depends on the pump. I think my Honda-engined Ryobi does 3300psi (3200?) and can strip wood off a fence at the narrow spray pattern.

We had to prohibit the use of high pressure washers getting the mud off military tanks as at too high pressures they'd penetrate the seals on the roadwheels and other parts of the suspension. Didn't make the troops real happy on the wash rack though but saved a lot of maintenance later. Changing a roadwheel ain't quite like changing a wheel on a car. I'd exercise caution under the car.

-- Chuck

 

I wouldn't let Chuck scare you off but nozzle tips do depend on pressure rating. Generally speaking, if the nozzle/pressure combo hurts your hand/skin then it's unsafe for your paint. Also, the obvious assumption is that you shouldn't be pressure washing at a very short distance. Start with 40 and then move on to 25 if needed.

 

My to-go nozzle is 20 degrees for getting the initial layer of dust off and something wider like 40 degrees for the final rinse with DI water. My pressure washer isn't that strong (1800psi) so I can get a little closer without damaging the paint than say someone with a 3200psi gas washer.

 

Not mentioned here is the actual pressure your washer is producing. I have a gas powered 3250 psi washer that I use for cleaning concrete ( at least once a month for the patio) blowing away hornet nests, trenching for landscaping, cleaning grills, doghouses, chickens areas, sheds, doghouses, houses, and more. I will never use it on a car. Too much potential for damage.

If you have a low pressure (electric) with a wide nozzle and you want to clean the mud from the underside, sure. Beyond that just wash the car the American way: by hand.

 

LOL We must be un-American

 

 

In case anyone is interested, today only!