Excessive dirt

[faraway]

.....Metal or plastic wheels didn't seem to make much of a difference.....

I have a story just for curiosity

Many years ago when I had a German based layout needed the tracks to be cleaned throughly and intensive. I got some kind of solvent on a cotton fabric and whipped all the rails. I use a lot of solvent to be sure to get all dirt removed for sure. The cotton got those nasty black stripes and the rails looked shiny as new.
I put an engine with some cars on the layout and it went on wonderful for some time. It went worse after some minutes and the engine got serve pickup problems within some minutes. After 10 minutes the layout was virtually useless. I looked at the fresh cleaned rails and they were covered with a thin black layer. It was even worse at gaps, frogs etc.
I had a lot of cars with plastic wheels at that time. You guess right, the wheels and the residual solvent became very good and intense friends and partially melted down in love......
No more plastic wheels for me please. It took me three days to clean the tracks from melted plastic!

Just a story many years ago and not related to the intense dirt about a year ago.