Coolants
1 800 255 4417
www.castrol.com/GPS
Background & Properties
July 2018
Important Properties: Coolant
The SCA prevents the following types of wear and cooling system problems: rust, oxidation, corrosion of iron and
steel components, pitted cylinder liners and water pump impellers. Pitting (also known as cavitation) is one of the
most common side effects of using antifreeze without SCA. During pitting, the liner vibrates away from the coolant,
creating an area of low pressure. This area causes the coolant to vaporize, leaving behind vapor bubbles that can
implode at pressures of 60,000 psi. This implosion can remove a chunk of metal liner in as little as 50,000 miles.
Radiator
Water
Pump
Cylinder Block
Thermostat
Housing
Cylinder Head
Water Bypass
Block
Heater
Oil Cooler
Cylinder
Liners
Coolant affects an overwhelming number of engine and cooling components as shown in the illustration above.
Problems resulting from leaks, over concentration or lack of SCA can affect these critical engine areas. To avoid
coolant-related problems, use a pre-mixed, pre-charged antifreeze and check for proper treat rates twice a year.
A test of the pH level, SCA level and freeze point can help determine the condition of antifreeze.
Aluminum vs. Iron-Based Cooling Systems
Cooling systems in cars and light trucks contain more aluminum parts—a much lighter weight metal—than iron
components. These aluminum parts require special protection from antifreeze by using performance-directed levels of
silicates in the formulation.
Heavy-duty gasoline and diesel engines are typically constructed with more cast-iron and have iron-based cooling
systems. The iron in the cooling system of heavy-duty engines requires additional iron corrosion protection that
antifreeze with higher silicate levels cannot provide. For this reason, an antifreeze that contains very low silicate levels
and more iron protection is preferred.
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