Why did my used Mobil 1 oil turn bright purple?!

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Is it because it wants to be Royal Purple when it grows up? No, seriously, I did an oil change yesterday. As usual, some spilled on the garage floor. I sprayed a general purpose heavy-duty “cleaner/degreaser” on the oil and it turned bright purple! I’ve never seen that before. I sprayed some on some new oil and it did NOT turn purple, so this means some combustion by-product or engine wear component reacted with something in the cleaning fluid and turned purple. The bottle of cleaner listed the following three ingredients, including these numbers: 2 Butoxyetanol (111-7602) Sodium Metasilicate (6834-92-0) Sodium Hydroxide (1310 730-2) Is there a chemist in the crowd who might know what turns purple when it reacts with one of the above chemicals? I recall hearing once that Chlorine turns purple when it contacts copper, is something like that going on? Do I have copper in my oil? I plan on sending a sample for analysis, but I won’t have the results for a week or so. Also, the analysis only checks for elements, and this reaction might be caused by some more complicated chemical that the analysis won’t show. I’ve been using a lot of fuel system cleaners lately and perhaps some type of solvent or other component got in the oil If it matters, the engine has been running really well lately and the magnetic drain plug had even less than the usual amount of fuzz on it. Thanks in Advance…
 
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Hey I am no chemist, but I would guess that this was a litmus-paper type reaction due to the sodium hydroxide (caustic soda). Litmus paper turns different colors based on the level of acidity vs. alkalinity. If I remember right, blue-purple is the color for alkaline(base) solutions. I have seen similar reactions with wine and (believe it or not) soap rings in the bath tub. Soap can also be caustic.
 
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Was the cleaner/degreaser Castrol Superclean? The numbers are CAS RNs (Chemical Abstract Service Reagent Numbers), which just identify the chemicals numerically rather than textually. Inorganic and organometallic compounds tend to be vibrantly colored. For example, copper (II) sulfate is a beautiful blue in aqueous solution... but it's really hard to say what you have just based on color.
 
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My guess is also the Sodium Hydroxide reacting with the calcium that has dropped out of solution in the base oil, whereas in new oil it may be in soultion and bound and not available to react with the cleaner . If those are the right chemical terms to use. On aside I know bleach cleansers will turn bright purple with spoiled milk too. But that may be from the bacteria and not the calcium...
 

kang

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quote:
Originally posted by NovaMan: Was the cleaner/degreaser Castrol Superclean?
Yes! How did you know? It was Castrol something, Superclean sounds right. I didn’t think the brand mattered. I know I’ve used this cleaner on used Mobil 1 oil before and I sure don’t remember the bright purple color. So the Sodium Hydroxide is a strong base? Does that mean my oil was overly acidic? Or just that the base was reacting with something like the calcium that had dropped out of solution or perhaps some combustion by-product? I guess another question would be what turns purple in the presence of a strong base? Or is that too wide of a question, e.g. a lot of things turn purple in a base. On another note, I cut open my oil filters (yes, both of them) after I made that post yesterday. Nothing of interest inside. No evidence of any debris caught in the filter.
 
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It was the nano-robots giving the signal that the cleaning job was done, and it's time to rinse. I wonder if you could create a dye that analyzes the TBN of an oil, and changes color when it gets below 1.0.
 
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quote:
Originally posted by Larry the Cable Guy:
quote:
Originally posted by simple_gifts: If it's purple and smells like twizzler's perhaps it should get it's own posting area.
[LOL!] [LOL!] [LOL!] That right there is funny.

Good one....LMAO.. [LOL!] [LOL!] [LOL!] [LOL!]
 

kang

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Worse things? What "worse thing" are you thinking of? I can think of a "good thing" that I certainly wouldn't want to turn purple! [Smile] [Smile] [Smile]
 

kang

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Thanks Pablo. So the base in the cleaner turned the dye purple. Makes sense.
 
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Castrol Superclean, in the purple bottle, seems to be caustic when sprayed on aluminum & alloys. While cleaning up around the oil fill tube, I oversprayed on the cast aluminum valve cover and the Superclean turned slightly white & bubbly, like a chemical reaction. As a result, I'm pretty shy about using it anywhere near any aluminum components.
 

kang

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Ut-oh, I sprayed some in my engine compartment, where the oil spilled. There are some aluminum parts in there. I didn't see any reaction, like turing white with bubbles, but perhaps I better flush the whole area out with water anyways. I only have a few ounces of the stuff left... I doubt I'll buy more...
 
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quote:
Originally posted by kang:
quote:
Originally posted by NovaMan: Was the cleaner/degreaser Castrol Superclean?
Yes! How did you know?

The ingredients gave it away. It's great stuff: the 2-butoxyethanol is probably in there to make organics soluble in aqueous solution (this results in a ternary phase system), and the sodium hydroxide basically destroys everything on a chemical level. The sodium metasilicate is probably in there as a buffer so that it doesn't lose pH as quickly while the brew is doing its job. Simple and effective. [Smile] After you spray anything with SuperClean (or any cleaner that contains an acid or a base), it's always a good idea to rinse the parts thoroughly with water after you're done cleaning. As long as you don't use an overly concentrated solution or let it sit too long before you rinse it off, metals should be fine... but it sure takes the shine off paint in a hurry! I like Pablo's idea of a pH-sensitive dye, but it only happened with the used oil...
 

kang

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quote:
Originally posted by Pablo: The dye in M1 is probably pH sensitive. Most oil dyes are. Under some pH probably brownish, over 10-12 or something, purple.
Hmmm, it occurred to me overnight that if the dye were the cause, then both the new and old oil would have turned purple. Since it was just the old oil that changed, I don’t think it was the dye.
 
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