In regards to the free gas-station wash, you get what you pay for. Many of those car washes use mechanical brushes, which will probably damage paint unless they’re being wielded by super-smart car-washing robots (in which case, the machines have already taken control). Most automatic car washes used recycled water too, meaning your prized ride is getting the same water applied to it as the rusty 1974 Plymouth Volare that went through in front of you. In addition, while filters will catch most particles, they don’t get everything, and they can’t filter out dissolved road salt and leaked automotive chemicals. Unless you’re driving your ex’s car, or you prefer to be scrubbed with recycled Plymouth rustwater, avoid the autowash.