I hate to recommend one particular brand of car wax because there seems to be a few good ones out there. The problems that we see nowadays are contamination from organic and industrial fallout IFO.
Because of the clear coat, we do not always see the signs and problems until we look closely at the paint and discover the damage.
There are above surface defects like organic and industrial fallout. There is bird, plant and industrial pollution like exhaust residue that becomes an acid when it is mixed with the dew of the early morning.
Above surface contamination requires a through hand car wash and a light paint cleaner like Meguires Dual Action Cleaner Polish #83 by hand or a orbital DA polisher and a foam pad to restore the paint surface; followed by a good carnauba paste wax without any cleaner in it.
Below surface defects in the paint can be much more problematic. Surface scratches tend to be further down past the clear coat. "Crazing" looks like fine lines in the paint but is actually a mechnical break down of the clear coat. This problem will require refinishing.
Some stains and blemishes, like light marring from shopping carts, can be fixed by carefully polishing and color-sanding the area affected area. I would recommend a special sanding paper from 1500 to 3000 grit depending on how deep the surface imperfection is. Measure first with a paint gauge to determine if there is enough clearcoat to to do this repair.
Clearcoats from automobile manufactures tend to be limited to 2 1/2 mills. Defects deeper than that and you just bought yourself a paint job.
The point I am making is there are a lot of good products out there. If you do not have an idea what to buy, contact the manufacturer and as them for their assistance.
If you keep your car as a weekend driver and have a place to store it, in most cases you will just need a pure polish with a light cleaner to remove towel marks, then a good carnuba wax (Zymol) with some nice micro fiber towels to do your work.
For cars that are used everyday, earns seek out the services of a professional auto detail service. Look for someone willing to advise you of the condition of your vehicle and willing to discuss a plan to take your car two or three times a year for a good through cleaning.
The margins of return are far greater on a car that looks new than on a similar car with the same mileage but no care. Who knows, some of the automobiiles we see being brought to market if properly cared for, could end up as another classic to park along with your SL.
Any comments please email to bobgeco@cs.com
Bob Geco