Coolants
1 800 255 4417
www.castrol.com/GPS
Background & Properties
July 2018
Important Properties: Coolants
Many engine failures are the result of improper antifreeze usage. To protect equipment from coolant-related damage,
it is critical to know the different antifreeze types, required mix ratios and problems that could result from improper use.
Coolant Basics
The glycol in coolant helps it ful ll its most basic function—freeze protection for an engine. Coolant is also expected
to provide a stable, cool environment for seals and gaskets. Using antifreeze in its concentrated form can result in
silicate or gel dropout, commonly known as "green goo," leaving critical engine parts unprotected. Water pump leaks
are also commonly attributed to an over concentration of antifreeze. A 100 percent antifreeze solution will turn to a
solid gel at 9°F (-13°C). For best all-around protection, use a 50:50 mixture of antifreeze and water. Concentrated
antifreeze needs water for a balanced chemical package and outstanding performance.
Antifreeze to Water Mix
Coolant should not be mixed with hard tap water. Hard tap water has excessive calcium and magnesium deposits that
can cause scaling, which will result in inadequate heat transfer. To avoid scaling, use only soft or de-ionized water that
is not treated with salts or chlorides when mixing water and antifreeze. (OEMs publish limits in parts per million [ppm]
for hardness, chlorides, sulfates and total dissolved solids for the water used to dilute antifreeze.)
Antifreeze Protection Chart
Freeze/Boil
Protection
40
50
60
-12˚F
-34˚F
-62˚F
222˚F
226˚F
231˚F
Freezing
Down to
Boiling*
Up to
Percent
Concentration
*At sea level. Boil point increase 3˚F for each pound of pressure exerted by cap.
Supplement Coolant Additives (SCAs)
Fresh antifreeze also requires a supplemental coolant additive (SCA) when used in heavy-duty engines. (Castrol
Radicool SF-O Premix Coolant does not require SCAs.) SCAs come in liquid concentrate or through a pre-charged
lter, and some antifreeze is already pre-charged with SCAs. The supplemental coolant additive is depleted during use
and needs to be added periodically to the coolant system. However, there is antifreeze available that contains the SCA
(pre-charged antifreeze) and the proper water to antifreeze ratio (pre-charged/pre-mixed). See Types of Antifreeze for
more information.
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