Lesson 5/Learning Event 2
In the summertime when there is no danger of freezing, plain water with a rust inhibitor added is used. The
inhibitor will reduce or prevent rusting and corrosion, but it will not remove rust or corrosion that has already
In the wintertime when the temperature falls below 32F, an antifreeze solution must be used in the cooling
system to prevent freeze-up. A rust inhibitor is included in the antifreeze mixture, so it is not necessary to add
the inhibitor too. Ethylene glycol and an arctic-type solution are two types of antifreeze issued for use by the
The ethylene glycol antifreeze must be mixed with water at the time of installation to lower the freezing point
of water. The best protection from freezing can be obtained from a mixture of 40 percent water and 60
percent ethylene glycol antifreeze. This lowers the freezing point to -65F. Although it may sound odd to you,
adding either more or less ethylene glycol to this mixture will raise the freezing point. Ethylene glycol
antifreeze solutions are used where the temperature is not expected to go lower than -55F.
In arctic climates where temperatures often go lower than -55F, the arctic-type antifreeze is used. It provides
freeze-up protection to -90F. Arctic-type antifreeze is premixed at the factory and is used full strength. It
should never have water or any other type of antifreeze added to it.
Other types of antifreeze containing alcohol or glycerin are made, but they should never be used in a military
vehicle unless it is an emergency. If they are used, they must be drained at the first opportunity and replaced
by an ethylene glycol or arctic-type antifreeze. Alcohol and glycerin antifreeze will boil and evaporate at a low
temperature very close to that of the engine's normal operating range. To use them, you must mix them with
water at the time of installation.