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"Why" silicone oil is great for rubber and Armor All isn't

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I recently made a post on my most widely used products for preservation and maintenance of my vintage Tamiyas. I did this to hopefully encourage others to post their favorite products so the rest of us may benefit from our collective knowledge.

With thanks to DJTheo and OCD for their links and input, I became aware of a degree of uncertainty regarding what is effective and safe for protecting the rubber on our Tamiyas. I have seen this same concern on automotive forums and soberingly, the same confusion. I posted this article as not a "How to" but more a topic of discussion. I believe the preservation of vintage rubber components is important for many of us. Link: http://www.tamiyaclub.com/forum/index.php?showtopic=26961


This post is intended to:

1. Present silicone oil as an appropriate protecting solvent for natural rubber products.

2. Support the theory that some Armor All (and many competitors) should not be used on our vintage cars (additionally, why they should be avoided).


I am unequivocally a man of science. By nature I am very analytical and I thoroughly enjoy research. You may notice my posts, aside from the obvious humorous offerings are sometimes long, detailed and analytical, in other words the stuff that bores some (I'm loads of fun at parties[;)]). I myself enjoy the scientific process. My primary profession for the last 18 years has been medicine. I am an E.R. and Family Practice nurse. I work directly with other providers relying on scientific processes to diagnose patients in both emergency and outpatient settings. Sometimes they are life or death situations, often they are not. It's all exciting to me.

Using Differential Analysis:

In my experience, the most important aspect in diagnosing a complex case with multiple variables is the differential diagnosis. This method is time tested and accurate. The basis behind it is; "The process of elimination eventually leads to the correct conclusion." In medicine many diseases mimic each other and can cause specific groups of symptoms. An example: Influenza is known to cause fever, headaches and general malaise. This is true, however, having these symptoms does not indicate you have the

flu. Why? It indicates you MIGHT have influenza. (You may very well have meningitis, encephalitis, bacterial sepsis..etc.) The definition for ignoring differential analysis

and instead making an assumption based on vague, cause-and-effect correlation is called malpractice. Unfortunately it happens more often than it should and not just in medicine. How does the "differential analysis" apply to the silicone/Armor All uncertainty?

Question: Has it been conclusively shown silicone is the causative agent in damage from Armor All and not one of it's "other solvents"? (A reasonable question. Why not asked?)

What is known:

1. Many solvents/chemicals attack natural rubber. Most are of petroleum origin. Examples: Gasoline (petrol), motor oil, WD-40, paint thinners, mineral spirits, naphtha, toluene and various other petroleum distillates.

2. Manufacturers of pure silicone spray oil unequivocally and blatantly recommend its use on rubber. Major manufacturers of treadmills and personal prophylactics (condoms) provide silicone oil as a lubricant accompanying their products.


Some believe Armor All products should be avoided for use on rubber (tires) because of the silicone solvent. I agree in the avoidance of these products but I ask: "How was it determined the causative agent is silicone?" more importantly, "Were the other chemicals ruled out?" (Differential analysis). Many so-called "silicone products" contain (significant) concentrations of rubber damaging solvents. (Rapidly dissipating propellants are an exception)

I. "Do not use (certain) Armor All products for natural rubber." (In Agreement)

Why? Referred to as a "silicone product", I think some may believe silicone is the only important or significant active ingredient. I believe this is incorrect. I've included links below of several Material Safety Data Sheets (MSDS) to Armor All products. I hope there is little misunderstanding of these "other chemicals".

MSDS 01: (Requires Adobe Acrobat Reader)


MSDS 02: See "Ingredients"


MSDS 03: From National Library Medicine/National Institues of Health (U.S.)


II. "Silicone spray oil is detrimental and not recommended for rubber." (Disagreement)

Why? From a chemical standpoint silicone oil is a synthetic polymer (Source: Dow Corning "The Basics of Silicon Chemistry", see below) as opposed to a petroleum derivative. It is unequivocally recommended by it's manufacturers for use on rubber. Manufacturers of treadmills and condoms use it. Not uncommonly it is the lubricant of choice.

This should lead one to ask the logical question: "If silicone oil degrades rubber, why do prophylaxis manufacturers place themselves in a position of inevitable litigation?" (Hopefully I needn't elaborate on all the potential STDs and unwanted childbirths that could occur from such a clearly negligent act.)

Dow Corning: The Basics of Silicon Chemistry


National Institutes of Health (U.S.): A randomized controlled trial comparing nonoxynol-9 lubricated condoms with silicone lubricated condoms for prophylaxis.


Gunk: M914 Silicone Spray (Google Cache)

CRC: 808 Silicone (Google Cache)

Permatex: Silicon Spray Lubricant (Google Cache)

To Learn More:

(The links below are offered as supplemental information and not to be assumed authoritative)

Silicone Grease:





1. I have found no evidence to support the theory silicone oil is damaging to natural rubber.

2. On the contrary, it is frequently the lubrication of choice by major manufacturers and may be the best commercially available product for protection of natural rubber.

3. Some known damaging "silicone products" (e.g. Armor All) have significant concentrations of "other solvents" including, but not limited to, petroleum distillates.

Obviously this is not the final word. However, I hope it clears some misunderstandings. Ultimately I wish to show silicone oil is not only appropriate but a highly recommended choice, supported by factual evidence (vs. 3rd party, anecdotal statements) for protecting our treasures. I hope this has been accomplished.

Doesn't your Tamiya deserve it?[:'(]

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Where could I obtain pure silicone oil ?

I can only find it as an ingredient in products such as Armor-all, I've never seen it sold by itself though.


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If you are into airsoft guns or know where to buy them you can probably find the silicone in the form of a spray can.  The spray can could cost you more.

 You may also want to check a motor vehicle supply store for ignition wire spray used for wet weather, which I believe is silicone in a big can and cost less but read the label and talk to a knowledgible sales person about the actual intended use.

Items made and used for RC are usually more expensive than similar items found in hardware of automotive stores.


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TC Tamiya,

OCD and myself use the same Napa brand as they are all over the

U.S.  I would guess you could find silicone lubricant spray at

your local automotive parts store??  I'm unfamiliar with chemical

laws in other countries, sorry[:(].  I do know it's reasonably

safe, it's used in the food industry here to lubricate machines that

come in contact with food products.

The three ingredients in the Napa-brand are Polydimethylsiloxane

(silicone oil), heptane and carbon dioxide (propellents).  The two

previous responses sound good.  I know my RC-10 shock oil is 100%

silicone.  It says it on the bottle.


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We use some product from this company as a defoaming agent for the pulp&paper industry.

To my knowledge, silicone(oil) is a "hardened" rubber with specific features so using it on it's basic compound (like rubber) it's only logical.

Pure silicone is very expensive (app. €125/kg), that's the reason why there's a low % in spray cans like Armor All or Cockpit Spray.

I hope this adds some to the discussion.

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Hard subject since we have to rely on 3rd opinions and especially www, personally trust book or scientic magazine articles more, but this needs too much "hunt" time.

Unfortunately you can find also opposite opinions on silicone like "The raw silicone oil that is the main ingredient

in most of the nationally advertised, auto parts store, high gloss products

may actually dissolve the wax and be the cause of premature tire sidewall

cracking/failure." http://www.autoeducation.com/carcare/tires.htm


I personally recommend glycerine as I haven't seen any negative reports on rubber about it, but maybe some of you will find something opposite and I be corrected.

I guess both silicone and glycerine are good choices as they are used in brake fluid which of course shouldn't attack the rubber hoses.


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The raw silicone oil that is the main ingredient in most of the nationally advertised, auto parts store, high gloss products may actually dissolve the wax and be the cause of premature tire sidewall cracking/failure." http://www.autoeducation.com/carcare/tires.htm<BR>

Yes, I heard that before but they always forget to mention that those product also contain other ingredients that could be the cause.

In fact, UV-light is also part of the deintergration of rubber, like heat, wear and dirt.

Silicone is an organic substance and can be affected by these things too so... I guess we'll never know until someone will test this over a period of 10 years and with these variable conditions.

Not me.

I use pure silicone instead of glycerine because I can use it on both metal and plastics.

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