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liquid-cooled engine above the dew point, water is being
constantly deposited on the cylinder walls and wiped down into
the crankcase. If this water is allowed to remain, acids are formed
that can seriously injure the engine.
The only way to prevent this is to keep the crank-case
temperature sufficiently high to drive water out of the crankcase
oil. On an engine operating indoors and protected from weather
changes an oil temperature of 150°F is sufficient. A drilling
engine, being out of doors and subject to weather changes, requires
C
a minimum crankcase temperature of 165 F. The top temperature
is not important so long as you stay within reason. A temperature
of 225°F to 250°F is permissible, 180°F to 190°F is ideal.
In checking the crankcase temperature is sure the
thermometer is well down in the oil. If it is held above the oil
level, a false, high reading will be obtained due to hot oil falling
off the pistons and cylinder walls onto the thermometer bulb.
Lubrication. Тhe fact that lubricating oils are constantly
being changed and improved indicates that lubrication engineers
are not satisfied with their own knowledge of the subject.
One change in the thinking regarding lubricating oils is
desirable ductility. Twenty-five or 30 years ago SAE 30 oil was
spoken of as light oil. Today an oil of the same viscosity is called
heavy oil.
Probably the most outstanding contribution to lube oils has
been the advent of the additive or heavy duty oils. Although they
are definitely an improvement, they also add certain problems,
principal of which is the problem of knowing when to change oil
in your engines.
Many operators use a laboratory test. Some have their own
laboratories. Others make use of commercial testing laboratories
that are available at reasonable costs. No lab report is infallible but
it is an indication.
A visual inspection will show only some oil conditions.
Probably the most important item and the hardest to detect in time

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