That really depends on what you call “old”.
Most cars built in the last several decades are layered with paint AND clear (several coats of each). Even cars older than that, if they’ve been repainted or otherwise repaired, will also be painted this way, and the process of caring for them is the same.
Very old cars (we’re talking 50-odd years and older), with original paint sometimes have single-stage paint, which basically means no clear coat, and the only thing protecting the panel underneath is the paint colour.
When it comes to those older classics, they demand more effort and frequency in keeping them clean, and polished, to protect them (using super-soft and gentle products, with regular waxing, depending on how often it’s driven).
So, unless you have a golden age, desirable classic in your garage, there’s fundamentally no difference between washing a 20-minute old car, and a 20 plus-year-old car.
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