How to pressure wash a car without etching the clearcoat.

This is the job sequence behind the car & driveway kit. It is the paint-safe half. The concrete pad still belongs to the driveway how-to. Which fan at your PSI is the tip size chart. Size the hole on the orifice chart, and read flow from a tip you already own on the GPM chart. Chemistry is the foam and soap guide. If the gun is threaded, the quick-connect wand guide is the fitting check before a QC tip or cannon will click on.

Why 40° is the paint tip

Clearcoat wants a wide, forgiving fan — the same idea as vinyl siding, with less ambition. White 40° is the pre-rinse and the final rinse. Green 25° can lift stubborn film on an electric or a homeowner-gas machine if you keep distance and keep the wand moving. At 3,500–4,000 PSI, 25° is too much. The yellow 15° and red 0° in a 5-pack are for other jobs. So is a spinning surface cleaner.

• Hold a foot or more with 40°. Closing in is how you etch clearcoat.
• 25° green only with more distance, and stay off edges and badges. Skip it on a prosumer machine.
• Keep the fan moving. A stalled tip leaves a track you will see in the sun.
• Confirm the hole on the tip chart before you click a pack. The car kit’s 5-pack is the listing rated 2.5 GPM at 4,000 PSI — check it against your stamped numbers.

PSI and GPM: electric vs gas

The fan does not get narrower because the pump is stronger. It gets farther from the panel. These are the same bands as the tip size chart and the foam guide. A 1.4 GPM electric can wash a car. It will not make shaving-cream foam.

• Compact electric. About 1.2–1.6 GPM in the 1,600–2,000 PSI band. Rinse with 40°. 25° only with distance. Under about 2 GPM a cannon mostly spits — use the soap tank.
• Strong electric. About 1.8–2.0 GPM and 2,000+ PSI. Light cling if you are patient. That is the car kit’s “1.8+ GPM” line. Same fans.
• Homeowner gas. About 2.3–2.8 GPM. The tip chart’s band is 2,600–3,200 PSI; the foam chart calls 2,800–3,200 PSI real foam. More standoff than an electric. 40° rinse. 25° only with distance, off edges and badges. Orifice 3.0 is the usual hole — confirm yours.
• Prosumer gas. 3.5+ GPM at 3,500–4,000 PSI. 40° white only, with extra standoff. 25° is too much on clearcoat at this PSI.

Color tips and the cannon are 1/4″ QC at the wand. Many electric guns are M22-14 or M22-15. Read the quick-connect wand guide before you order brass that will not click on. A 12–20″ wand is the nimble length for a car.

Foam, dwell, then the mitt

Foam is a dwell tool. It loosens film so the mitt is not the first thing that meets baked grit. Pre-rinse with 40° first. Apply in the shade, bottom to top on the vertical panels so the mix does not dry in streaks as you work up, and dwell a few minutes. Do not let it bake. Flush the cannon with clean water when you are done. The chemistry path — what can go in the bottle, and why bleach cannot — is the foam and soap guide.

Then the two buckets. One holds the cannon soap, diluted the way the bottle says. The other is clean rinse water. Load the mitt from the soap bucket, wash a panel, then rinse the mitt in the clean bucket and wring it before it goes back in the soap. Grit stays in the rinse bucket instead of going back on the paint. Top to bottom. The washer’s last job is the 40° rinse, not a substitute for that pass.

What to stay off

• Chipped paint. Water driven under a stone chip or a failing edge lifts clearcoat. Rinse past it. Do not dig at it with 25°.
• Badges and trim. Emblems, antenna bases, and edges sit proud of the panel. A close fan peels them. Keep the standoff you used on the flat panels.
• Door seals. Do not park the tip in a door gap, on window felt, or in a sunroof drain. A close fan peels weatherstrip and pushes water into the cabin.
• Engine bay. Skip it. A fan into the bay drives water into connectors and the intake. That is a different job.
• Hot sun. Wash in the shade, on panels that are cool. Soap on sun-hot paint bakes into streaks.
• Wheels, carefully. Do them after the paint so brake dust does not ride back onto a clean panel. Painted and coated wheels stay on 40°. A 25° green can reach a wheel well if you keep standoff and keep moving. Do not pin the fan on a caliper, a brake line, a sensor, or into a bearing.

Leave the pad to the driveway kit

The car sits on concrete. The pad is a different fan, a surface cleaner, and a downstream degreaser — the driveway how-to. Leave the 15° yellow and the spinning deck on the concrete.

Picks that match this job

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Full short list, machine band, and danger notes live on the car & driveway kit. Chemistry path? See foam cannons and soap. Which fan at your PSI? Tip size chart. Electric gun that is not 1/4″ QC? See quick-connect wands. Washing the pad the car sits on? How to pressure wash a driveway.