Tar baby,
Coking may not be the most accurate term, but most of us use it, cause most of us (me included) are not chemical engineers.
The vaporization tubes are tubes through which the injection needles pass through. The injection tubes are sometimes referred to as "sticks', when in fact they are hypodermic sized stailess steel or maybe by now, inconel tubes. A tube is always hollow, but a stick might not be.
There is also a heating tube through which the injection tubes are passed which provide a heating area surrounding the injection tubes in order to promote complete vaporization of the jet fuel prior to it's reaching the combustion zone. You may have heard some engines that, while at idle RPM, make "snapping" or "popping" sounds. That may be caused by incomplete vaporization, and the sound is from fuel droplets exploding in the comustor. As the RPM is increased, the temperature is too, and the fuel is then completely vaporized. No more "popping".

The tubes also enable the engine manufacturer to "Tune" the engine. In other words, they can move the injection tubes around, by careful bending of the tubes, changing the angles at which the fuel vapor is admitted into the combustion zone, in order to have a flame front that is constant around the diameter of the combustion zone. Even combustion around the entire inner surface of the combustor is what must be done in order to avoid hot spots in the combustor. Maximum combustor/engine life, and good power is what the whole thing is all about. Just like a gas stove burner, in theory. All of the flames must be even in length, and the correct color.

Anyway, some folks say that the combustion by-product-crud-*&^%#@*^ found in the combustion zone and on the tubes, sticks, or whatever you choose to call them, is "Coke".
Coke is either Coca-Cola, an illegal substance some put in their noses, or as the term is used in the steel or metal alloying industry, a fuel made from the heating of bituminous coal in a furnace and a distillation process. It burns at a much higher temperature than the coal from which it is produced.

The black crud in our combustor area may not really be "coke", but I don't care. I use the term cause everyone else does.
Some think, or believe that 2380 forms more "coke" in our engines than some other oils do. That's okay with me too. I am using 2380 right now, as I got one heck of a deal on it at my local FBO.

Jetcat recommends Aeroshell 500, as well as AMT USA. In they're opinions, it is better oil for that reason as well as other reasons.
That's fine too. I believe their recommendations. I have used many of the oils, and feel that they are all good and they are all useable, as long as they comply with MIL-PRF-23699.
If anyone disagrees with me on this issue, that's fine too. I get very good bearing life in my JetCats.


Harley Condra
BVM REP
JetCat REP