I am always pushing you should never wash a mustang with pressure washer, car wash or even running water. You feet the rust inside the cowl, doors and quarters. No driving it does not help. The sealer inside those areas was put on raw steel before primer. Over time it cracks so when water is there is goes to bare metal and feeds the rust. No reason for all the soap and water the car is never really dirty. Clean water in a bucket and micro fiber towels and just wipe off. You will not feed the rust, wear the paint out or wash your wax off. My 73 has not had running water on it in 38 years now and waxed twice and never buffed. That is original paint and original black on the hood.
I think the washing of the car is more of a mental thing that a need for the car, lol.
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