"(You may also see a gradual accumulation of waxes and resins in the condensate that may settle out.)"
If sludge isn't the correct technical term for the stuff that settles out, what is the correct one?
Sludge is a reasonable term.
The point I was trying to make is that very light crudes (e.g. Shale oils) don't lead to significant resin/wax/asphaltene deposition. Over a large volume it may become significant, but it's unlikely to be a major issue for rail cars transporting them.
Tiny accumulations of waxes are unlikely to cause a problem except over many (hundreds?) of rail cars.
A bigger concern would be the use of Petrozene itself in a rail car that will ultimately contain a very light crude. Petrozene's composition has a significant portion of a class of compounds that will drop out of solution in the presence of a light crude. So if even a small amount of petrozene remains in a car, it will almost certainly form some "fresh sludge" when light crude is added - sludge that will need to be removed.
So, from that perspective, maybe this does represent a big market for Petrozene. Petrozene cleans up a small amount of sludge, then residual Petrozene forms fresh sludge that needs more Petrozene to remove. Lather, rinse, repeat.