What is the best product to use as a car wash? The correct answer is use what you like best. There are some drawbacks to certain products and advantages to others. Dish detergent (Ivory Liquid, etc) may be used, but realize that this product is designed to remove animal or vegetable fat/grease from fired ceramic dishes. It looks at your BMW's nice coat of wax with the same hungry eyes. If you enjoy washing and rewaxing weekly, then this is for you. Wax retailers love people who use dish detergent (they send the Ivory Company Christmas cards every year)
If you prefer to have your wax last a little longer, you may consider using a product that is specifically designed for automotive use. The quality products are based upon detergents instead of soaps. Soaps are manufactured from rendered animal by-products (the stuff the dog food people reject). They contain trace elements that can actually damage your paint. These trace elements are the same goodies that leave a ring in your bath tub. (Ring around the BMW)
Quality car wash/shampoos (same thing - most cars don't have hair) are usually pH controlled, contain gloss enhancers and some even have a small amount of water soluble wax for good measure. Use only enough car wash to break the electrostatic/ionic bond between dirt and your BMW. Start with a clean large bucket (preferably plastic - if you kick the metal bucket, Mr. paint chip rears his ugly head), add a small amount of the car wash and fill the bucket with cool water. Avoid hot water as it will soften the wax. Read the directions on the car wash bottle and try reducing the recommended amount by half. The more car wash, the more wax you remove. My personal favorite car wash is Sonax Gloss Shampoo and I use 3/4 of a capful for 5 gallons of water. Try to avoid powder car washes, as the undissolved granules can get on you sponge or towel and scratch the paint surface.
Make sure that your BMW is in the shade and the paint surface is relatively cool. Rule of thumb # 1: If you can comfortably hold your hand on the hood, you can wash/wax the car.
Spray the car with a gentle spray to thoroughly wet the surface. Don't use a 200 P.S.I. fire hydrant spray, it isn't needed and may grind the surface grime into the paint and cause scratches. Some of the concour purists will not use a nozzle on the hose at all. Start at the top of the car and work down. Rewet the top, gently wash the top and then rinse. Move onto another section, such as trunk or hood. Rewet this area, wash and rinse. Continue on down the car, completing a section at a time. This way, the car wash does not dry on the paint.
You may use a wash mitt, towel, or sponge to wash the car. I prefer a wash mitt as the grit tends to work up into the long fibers and not scratch the paint, When I redip the mitt into the washbucket, I give it a swirl to release the grit. The flat surface of a sponge can sometimes catch dirt and act like a sandpaper. The purist will use two wash mitts. One for the top half of the car (the cleanest) and one for below the trim line and wheels/wheel wells.
Your BMW should be dried as soon as possible. There are several methods to accomplish this. Lots of towels are a great drying medium. They should be 100% cotton (some of the blends contain polymer fibers that scratch). Start at the top, lay the towel on the top and then **gently** blot the towel on the surface of the paint to pull the water from the surface. Change to a dry towel and blot any remaining water. Move to the hood or trunk and repeat. Dry the sides last as the water will usually take care of itself on these surfaces. Another method is to use a chamois. There are two types, natural and synthetic. The natural leather chamois contain acids, primarily tannic, that strips wax. Most synthetic chamois don't seem to do a satisfactory job. One exception the P21S Super Absorbing Drying Towel. I have stopped using towels after trying this goodie. I used to be a "dyed in the wool" towel man. Driving the car to dry it may be fun, but you are redepositing dirt on the wet surface and allowing the resulting "mud" to dry on the paint.
I hope that the above brief synopsis rinses away some popular myths. If there are any questions or you can't find the products locally, please give me a shout.
Author: Larry Reynolds
Car Care Specialties, Inc
New Jersey Bulletin New Jersey Chapter April 1996