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Castrol Radicool Si-OAT
Castrol Lubricant Oils Company Logo

Antifreeze and Coolant for longer life


Castrol Radicool Si -OAT is a nitrite, amine and phosphate free antifreeze coolant with added silicate for the latest vehicles requiring silicate containing OAT technology. Aqueous solutions of Castrol Radicool Si-OAT act as both antifreeze and coolant and offer excellent corrosion protection to all metal parts found in the cooling systems of internal combustion engines.


Castrol Radicool Si-OAT protects for up to 3 years and has the following benefits

  • Excellent low temperature protection
  • Provides superior protection against all forms of corrosion
  • Eliminates deposit formation , because of its phosphate free formulation
  • Approved for use in Euro 6 trucks Castrol

Radicool Si-OAT is formally approved by MAN for use in those vehicles specifying MAN 324 Type Si -OAT coolants , including those vehicles built after Dec 2012.
It is also suitable for use in older vehicles previously using MAN 324 Type NF and MAN 324 Type SNF fluids.

This fluid is recommended for use in the latest VW, Audi, Seat and Skoda vehicles . It is also compatible with older VW TL774C(G11) and VW TL 774F (G12+) type fluids and can be used where VW TL 774J (G13) fluid is recommended.

Castrol Radicool Si-OAT is suitable for use in Mercedes Benz heavy duty vehicles manufactured after 10/2011. It is not currently
recommended for passenger vehicles.

This coolant should be used at concentrations of between 33% and 50% in distilled water. For optimum performance it is recommended to use at 50% concentration to significantly reduce the likelihood of wet cylinder liner pitting due to ‘cavitation erosion’. This form of corrosion erosion is caused by the implosion of air bubbles present in the coolant and which are attracted to the liner outer surface.

When the bubbles implode, minute amounts of liner material are removed from the surface, and if allowed to continue unchecked, will result in liner porosity and severe engine damage.

Name Method Units Castrol Radicool Si-OAT
Density @ 20C, Relative DIN 51757 g/ml



Water ASTM D1123 % wt 2.6
pH, Engine Coolants / Antirusts


ASTM D1287 8.5
Alkalinity, Reserve of Engine Coolants


ASTM D1121 mg KOH/g 9.7
Freezing point ( 50% vol dilution in water)


ASTM D1177 °C -38.0
Appearance Visual Clear, Magenta

ASTM D3306 (I)
ASTM D4985
MAN 324 Type Si-OAT
MB-Approval 325.5
VW TL- 774G


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