[shorod]

If you're really trying to get the car clean, this is not a good way to do it. For starters, using high pressure on dirty paint will force dirt particles in to the clear coat/paint and may cause more damage than if you just left the car dirty. There will often be grime on the vehicle that will require more agitation than high pressure rinsing to remove.

If you're talking a typical car or truck, my suggestion would be to just use a garden hose with an adjustable nozzle set to "Shower" to moisten the paint finish. Then use a good automotive car wash soap to sponge down the car and remove the dirt, followed by a final rinse. The "Shower" setting should be fine for the final rinse as well.

If you're talking a large RV or tractor/trailer, then you may be limited to something like a power washer to get all the surfaces wet.

-Rod