The silver state. [volume] (Winnemucca, Nev.) 1909-1925, 1915-08-07
CARBON FOUND
IN MOTOR OIL

Lieutenant g. 8. Bryan, government
expert, in an article in the February
issue Of the Journal Of the American
Society Of Naval Engineers, says:
carbon may exist in a motor oil in
two forms: First, as free carbon held
in suspension, and, second, in combi-
nation with hydrogen, forming the nu-
merous hydrocarbon compounds which
60 to make up the OIL The amount CT
free carbon in a well-refned oil is very
small, and the Objectionable carbon de-
posit is generally due to some other
factor.
"The conditions attained in the cyl
inder of internal combustion engines
that result in the formation of carbon
are: First, high temperature, and, Sec
ond, a limited supply of oxygen (air).
References have been made to oil
burning This term has been used
rather loosely, as strictly speaking,
burning means the combining of the
vapors from the oil with the oxygen
of the air, and does not include SIM
rie vaporization of the OIL Unless air
is present in excess of that required
for the combustion of the gasoline or
fuel oil, and usually il is not, the oil
cannot really burn. Under the intense
heat, however, the inner surface Of
the oil film will be vigorously affected,
and, in the absence of the air neces-
ssry for burning, three things may
happen.
cease l. The compounds may vola-
tilize with decomposition.
cease 2. The compounds may decom-
pose with the formation of free car
ben and hydrogen.
"Case 3. The compounds may decom-
pose with the formation of other hy-
drocarbon compounds of a different ma
ture.
"The products formed in case ! give
no trouble, rs being gaseous, they are
carried out with the exhaust, whether
burned or not. OF the products formed
under case 2, the hydrogen would pass
out of the exhaust, whether burned or
not. The carbon may be blown out
with the gases or may remain in the
cylinder. Whether or not il remained
in the cylinder would depend greatly
on the condition of the oil film on the
cylinder walls. Some oils form a thick,
viscous gummv deposit, which retains
the carbobn formed on its surface and
prevents it from being blown out
through the exhaust. This gummy de-
posit gradually gets thicker and hard
er, eventually forming the hard car
bon deposit so well known in cylinders.
"This gummy deposit is due to the
action of the compounds mentioned in
case 3. The free carbon liberated in
case 2 is light and fluffy, and of itself
would not form the hard deposit. Where
the compounds break up into new com
pounds, however, some of the new com
pounds are volatile, while others are
heavier and more viscous than the
original compound. Continued action
Of the kind mentioned in case 3 win
therefore result in the gradual thick
ening of the film, and the retention and
absorption by the film of the carbon
that is liberated viii increase this ef-
feet until, finally, hard, brittle de-
posi- results.
"In the absence of any gummy de-
posit of this kind to cement the free
carbon together, the latter will gener-
ally be blown out through the ex-
haust. The oil that will give the best
results, then, is not necessarily the
one that will form the least carbon,
but the one that will form the least
carbon in the cylinders.
coils made from asphalt-base crudes
have shown themselves to be much bet
ter adapted to motor cylinders, as far
as their carbon-forming proclivities
are concerned, than are the paraffine-
base Pennsylvania oils
u.