Got this from another newsgroup. Could be the answer to Rotary plug fouling when using 100LL exclusively. Use care though, new stuff often has unexpected outcomes. You know? 

-al wick
Artificial intelligence in cockpit, Cozy IV powered by stock Subaru 2.5
N9032U 200+ hours on engine/airframe from Portland, Oregon
Prop construct, Subaru install, Risk assessment, Glass panel design info:
http://www.maddyhome.com/canardpages/pages/alwick/index.html

As promised, I’m reporting back on fuel additives.

I have spent a lot of time over the last six months researching most of the additives used as ingredients in fuel additives and quite a bit of time doing engine testing.  I used an air cooled, low compression, fixed timing magneto ignition engine for tests.  I removed the cylinder head after each test and took digital pictures of the head, piston and plug.  I only used 100LL as fuel.

Here are my results; on some things I can’t get too specific because they have become proprietary.

Starting at the simplest additives, here are the ingredients of Marvel Mystery Oil.  I shall call it MMO as an abbreviation.

Hydrotreated naphthenic oil

Paraffin oil

Oil of Wintergreen (methyl salicylate)

Red dye

This stuff was invented, as the bottle claims, in 1923.  Back then engines were rather primitive and so it this mixture.  The active ingredient is the naphthenic oil; the rest is just for dilution or to confuse the opposition.  Naphthenic oil was used originally as a low cost “once through” oil in IC engines or compressors with either no recirculating oil system or a poorly operating one.  The oil has marginal oxidation resistance so it is rapidly degraded and can only be used in once through systems.

In my engine testing it left the combustion chamber looking sooty.  Subaru engines operate hotter so it probably burns off this soot, so this is probably less of an issue.  The best benefit that could be obtained is valve guide lubrication and upper cylinder lubrication.  At 4 ounces per ten gallons it is not very economical.

Next in line is a whole slew of solvent based brews used as clean up additives.  These use toluene, xylene, trimethyl benzene diluted with paraffin oil and solvent naphtha.  Simple amines are used sometimes, as in Redex.

In engine testing these tended to clean up the inlet valve and fuel injectors, but it was a slow process.

TCP additives evolved from this type of formulation.  Tricresyl phosphate was diluted with toluene to make Alcor TCP.  This is used to alleviate lead contamination of spark plugs and exhaust valve seat recession due to the presence of lead in leaded fuels.

Decalin TCP does not use toluene, it uses ethylene glycol as a diluent which is far less volatile and so it is safer to use both from a toxicological standpoint and carrying it in the cockpit.

In my engine testing, a high dosage of Decalin TCP tended to leave yellowish deposits of lead phosphate in the combustion chamber and on the exhaust valve.  At the recommended level of ½ ounce per 20 gallons for Subaru’s the deposits were negligible.

The next generation of fuel additives took a quantum leap in performance with the addition of polyetheramines.  This was patented by Chevron in the mid 1980’s, but the patent expired three years ago.  Since that time there has been an explosion of products containing this additive.

I had a lot of trouble getting hold of the raw material polyetheramine since the manufacturers are picky about who they sell it to; but finally, in the interest of bringing you the very latest stuff I persevered (walking ten miles into the wind through three feet of snow uphill both ways, bring on the violins) and then I put it to the test.

I first “dirtied up” the engine by using a high dosage of MMO. 

Then I added a bit of polyetheramine concentrate to the fuel tank and ran the experiment again.  The effect was remarkable.  The combustion chamber and piston were very much cleaner.  I could not believe it and ran the test again.

I then ran a whole series of tests, comparing and mixing with Decalin TCP, MMO and other fuel additive brews that I bought at the auto store.

I used a great many head gaskets in this testing and the local supplier must be wondering what I’m up to.

The bottom line is that I am reformulating Decalin TCP to include polyetheramine.  This will make it a super product and I will call it Decalin TCP Plus.  The price remains the same.

Also, I will bring out a separate product called Decalin DeeCoke for combustion chamber, fuel injector, inlet valve and inlet manifold cleanup.  This stuff is so good that you only have to use it once every 50 hours by dosing at 5 ounces per 10 gallons.  It will be in a 16 ounce bottle, priced at $11.95.

You can use it at a maintenance level of ½ ounce per 10 gallons at fill up and then you would not need the 50 hour dose.   High dosage has no detrimental effect on the engine that I could see, and other manufacturers report the same thing.  The ingredient is on the EPA list of approved fuel additives.  It can be used in cars also.

It will be a couple of weeks or so before I can get bulk supplies delivered to make these new products, but if you are interested in this product please let me know.

Chris Lowery