Chevrolet Fleetmaster Series 1947 Owner's Manual page 51

A slight amount of these gases pass the pistons and rings,
even under the most favorable conditions, and cause the forma-
tion of water in the oil pan, in a greater or less degree, until the
engine becomes warm. When the engine becomes thoroughly
warm, the crankcase will no longer act as a condenser and all of
these gases will pass out through the crankcase ventilator system.
Short runs in cold weather, such as city driving, will aggravate
this condition.
Corrosion-Practically
all present-
day engine fuel contains a small amount of sulphur which, in the
state in which it is found, is harmless; but this sulphur, on burn-
ing, forms certain gases, a small portion of which is likely to leak
past the pistons and rings and, reacting with water, when present
in the crankcase, form cor,:osive acids, The more sulphur in the
fuel, the greater the danger from this type of corrosion. This is a
condition which we cannot wholly avoid, but it may be reduced
to a minimum by proper care of the engine.
As long as the gases and the internal walls of the crankcase
are hot enough to keep water vapor from condensing, no harm
will result; but when an engine is run in low temperatures, mois-
ture will collect and unite with the gases formed by combustion;
thus, acid will be formed and is likely to cause serious etching or
pitting. This etching, pitting or corrosion, when using fuel con-
taining considerable sulphur, manifests itself in excessively rapid
wear on piston pins, camshaft bearings and other moving parts
of the engine, oftentimes causing the owner to blame the car man-
ufacturer or the lubricating oil when in reality the trouble may be
traced to the character of fuel used, or a condition of the engine,
such as excessive .Qlow-by or improper carburetor adjustment.
s.
A. E. Viscosity Numbers -
The
viscosity of a lubricant is simply a measure of its body or fluidity.
The S.A.E. viscosity numbers constitute a classification of lubri-
cants in terms of viscosity or fluidity, but with no reference to
any other characteristics or properties.
The S.A.E. viscosity numbers have been adopted by practi-
cally all oil companies, and no difficulty should be experienced
in obtaining the proper viscosity grade in the different types of
motor oils to meet seasonal requirements.
The viscosity grades of oil on page 50 are recommended for
use in the engine of your car.
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