Frequent washing in an automatic touch less carwash can cause distortion of the outer surface of the windshield, door, or back window glass, according to General Motors. These types of car washes spray chemicals on the vehicle under high pressure, and do not use moving strips of fabric.
The wash solutions contain hydrofluoric acid which in some causes is not buffered correctly and after repeated exposure can cause visual distortion of the glass. The distortion takes on a
subtle orange-peel pattern, sometimes looking like a drip or sag etched into the surface of the glass. The damage will be first evident as a line on the glass where the wiper blade contacts
the glass. Once the glass is damaged, it can't be restored with scraping or polishing, and must be replaced.
Many people bring their own highpriced motor oil, (e.g. synthetic oil) to
have installed in their vehicle, instead of purchasing the bulk oil from the shop. If you bring your own oil, make sure the mechanic that changes your oil actually puts your high-priced synthetic oil in your car and doesn't wind up keeping it for his own use. While there's no guarantee that your own oil will get installed in your engine, there are a few things that you can do to increase the probability. If possible, look in at your vehicle while it's being
serviced. Watch from the waiting room, or stand by the shop entrance. If this isn't possible, ask to have your empty oil containers returned to you.