Brown speckles began appearing all over my white yukon. The dealer said rail
dust, fix with claybar treatment, $300 thank you! The spots started to come
back within 2 weeks. The GM dealer now does a tap dance and with lot of BS.
Who can I take this vehicle too to find out what is really happening to
this paint job. No other cars where I park this car are similarily
I am guessing you are in the mid-atlantic region. I too have seen the little black spots on my car. My spots looked like little balls of tar and you can scratch the tops of the ball off, but a small spot still remains which is hard to remove? Is this what you are seeing? If it is, you problem is not rail dust, but Artillery Fungus ! Yes I said fungus. In the mid-atlantic region there has been a real problem with this little known fungus which shoots a sticky liquid from it's insides up to a couple of feet away. The wind can then carry them even further. They grow in rotting wood and mulch. It may not be from your place of business, but rather from your house, or even the gas station you may visit every morning for coffee. (if they have mulch around)
For more information, Dr. Donald D. Davis of Penn State is currently doing research on this annoying fungus http://www.personal.psu.edu/faculty/d/d/ddd2/
My method of removing the spores is this... I wash the car first, then use bug and tar remover with a 100% cotton towel, as to not scratch the paint. This works well with spores that have not been on the vehicle for a long time. Older spores need to be removed with a clay bar, as your dealer did the first time. You can purchase a clay bar kit in most auto parts stores, under the Mothers brand. A word of caution with the clay bar, keep folding it over, exposing new clay, to prevent built up dirt from scratching your paint. It's a great way to clean your car, but if not used properly, it becomes like sand paper. I have also had limited success with latex paint remover sold under the M-22 label, but I do not believe this is sold anymore.
To prevent the spores from coming back, you can try to re-mulch the area that you park next to, or replace the mulch with stones as I did at my business.