From what I know. Very harsh chemicals are used at car washes. Look at the empty 55 Gallon drums in the parking lot used for traffic control. They have an #8 black diamond corrosive sticker. In most cases it's on all the chemical except the glass cleaner. I am in the Jan/San commercial chemical business so I know a little about these. They are classified as HAZMAT 9Hazardous material) They do this becasue they do not want to have to re-wash the dirtiest cars 2X. Most people who go to car washes only look for dirt. Not concerned about LSP being removed. This stuff is like Dawn on steroids. There are the foam washes that are more mild, with the guy standing in the tunnel. Still very hot products-not neutral.
If you really cared about your finish why would you take it to a place that uses the same towels to wipe wheel well lips and then moves to your hood!
If a car wash did a great job the way TID spec'd it. It would cost $ 25-40 dollars minimum and they would go bankrupt bc nobody would be there.
Car washes are for the masses. I have not been to one on over 7 years with the exception of my winter car a Silver 2001 QX4 that I will run through sparingly. I came back form Skiing in Vermont and my car was a salty mess. I could not ONR it bcause there was too much gross soil. I opted for a touch free wash no wax, no wheel cleaner and zero drying. Pressure wash and into the tunnel. I had many, many coats of Ultima PGP topped with 2 IW845. Seemed to make it OK through the winter but I feel guilty sending it through the tunnel every time I do.
If you were going to polish you are and it was shot already, I run it through, no wheel cleaner, no drying. They when you got home and re washed it most of the big stuff would be gone, but that is it for me.