Chevrolet Light - Page 76

Oil Pressure Gauge. When starting a co ld engine, it will be noted
that the oil gauge, on the instrument panel will re gister a high
oil pressure. As the _ engine warms up, the pressur e will drop
until it reaches a point where chan ges to higher spee ds will
raise the pressure very little, if at all.
If the oil pressure registers abnormally high after the en-
gine is thoroughly warmed up, an inspection should be made
to ascertain if the oil lines and passages are "plug ge d" up.
When to Change Crankcase Oil Oils have been grea tly im-
proved, driving conditions have changed, and improvements
in engines, such as the crankcase venti lating system, have
grea tly lengthened the life of good lubricating oils. However ,
to insure continuation of best performance, low maintenance
cost and long engine life, it is necessary to chan ge the crank-
case oil wheneve r it becomes contaminated with harmfu l for-
eign mat er ials. Under no rmal drivin g conditions, draining th e
crankcase and replacing with fresh oil every 2000-3000 miles is
r ec ommended.
Under the driving conditions de scribe d in the following
paragraphs, it may become necessary to drain the crankcase
oil more frequently.
Frequent long runs at high speed, or continuous driving
with heavy loads, with the resultant high engine operating tem-
peratures, may oxidize th e oil and may resu lt in the formation
of sludge and varnish. While no defi nite drain periods can be
recomme nd ed under these conditions, they should be more
frequent than under normal drivin g conditions.
Driving over dusty roads or through du st storms introduces
abrasive mater!pl into the engine. Carburetor air cleaners
d ec rease the amou nt of dust that may ente r the crankcase. The
frequen cy of draining depends upon severity of du st conditions
and no definite draining periods can be recommended, but
sho uld be more frequent than under normal driving conditions.
Short runs in cold weather, such as city driving , and ex-
cessive idling, do not permit thorough w arming up of th e
engi
ne and water may accum ulate in the c rankc ase from con-
de nsation of moisture produced by the burning of the fuel.
W.ater, in the crankcase, may freeze and interfere with proper
oil circulation. It also promotes rustin g and may cause clogging
of oil
screens and passages. Under normal driving conditions
this water is removed. by the crankcase ventilator. But if water
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