Purple residue from cleaning

[Okanogan]

I started using Mobil 1 0-16w synthetic oil as lubricant after it was suggested I was running my AR platforms too dry. After sitting for more than 6 months, some of the platforms looked like the oil was getting gummy so I decided to clean the firearms. I used KG carbon cleaner in the process as some of the guns had been fired a few times either before or during hunting season. On most of the weapons, I observed varying amounts of a purple residue on the cleaning towels. The platforms mostly have a black finish that isn't bluing but is probably some more modern equivalent. (It doesn't appear to be cerakote.)
Does anyone have the chemical background or experience to tell me what the reaction is that is producing the purple. (I'm making the assumption that it isn't a good sign and so skipped application of the synthetical oil after cleaning.)

 

[3chester]

Some oils have a marker dye in them for identification. Not sure if that's what stained Ur metals there tho.

 

[Laelkhunter]

No idea, but I doubt that the Mobil 1 is the cause or the problem. Just make sure that it is full synthetic and not a blend. We use Mobil1 for a lube when doing lots of firing during training scenarios and find it doesn't burn off or migrate like lesser (CLP) products. You are right, you want to keep it well lubed as opposed to too dry.

 

[Okanogan]

The oil itself appears to have the same light color you'd expect with motor oils. The KG cleaner fluid is also light yellow, about the color of pilsner beer.

 

[Laelkhunter]

Just to mention, there is a synthetic motor oil (well known in my area) called Royal Purple. It is purple. Any chance you (or someone else) put some of that in your gun lube bottle?

 

[Okanogan]

I'm using Mobil 1 0-16w advanced fuel economy full synthetic. I had been using a slightly heavier Mobil 1 0-30w synthetic but switched to the lighter stuff when I saw it on the shelf.

 

[3chester]

LSA, don't worry about the white smoke coming thru the top vent, they just an indicator she's running fine.

 

[Hugnot]

Motor oil contains:

surfactants (plural noun)

1. a substance which tends to reduce the surface tension of a liquid in which it is dissolved.

This stuff enables the liquid, like synthetic oil in this situation, to float away and suspend various particles that would be deposited on internal surfaces. In the situation described it is likely this is a "direct impingement" AR where gasses containing bullet, primer, and powder residue are diverted back via gas tube to provide impulse force to operate the bolt carrier. The residue stuff would have color, and this would be seen on cleaning rags.

I like to use motor oil as a cleaning agent but stop at using it as a lubricant.