When I wash my 9 year old, economy compact sports car to get bird poop and tree sap off of it, I use dish soap. I use microfiber sponges that I've been using for over a year now and dropped on the ground multiple times only to rinse off, and I'm never consistent about wiping in circles vs. straight lines. Afterwards, I use wax out of a 9 dollar bottle that I found at AutoZone. And when I'm done, my 9 year old economy compact sports car looks better than 99% of the cars in my town of 90,000 people.

Sometimes perfection has to give way to practicality. I don't have 12 hours to spend on my car and I don't have more than about 40 dollars to drop on cleaning products. Dish soap is an excellent general detergent and it works a lot better in preserving the finish of a car than bird poop or tree sap do. While I can always appreciate a theoretical discussion on the perfect car wash and I can certainly appreciate the scientific method being used here to observe the effects on a car's finish, I think it's important to bear in mind that most of our audience (drivers of a car that hasn't been produced since 2005) probably isn't looking for a top of the line detail.