Name: Castrol Radicool Si-OAT
Brand: Castrol

Summary

Castrol Radicool Si-OAT coolant data, from Castrol's own source. Castrol Radicool Si-OAT is a concentrate Si-OAT coolant listed by Castrol (bp). The manufacturer lists 5 OEM or industry spec codes, including MAN 324 Typ Si-OAT. Stated service life: protects for up to 3 years.

Disclaimer: General information only, not professional advice. Always use the coolant specified in your vehicle owner's manual. Using the wrong coolant can damage an engine.

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Specifications

Brand	Castrol
Maker	Castrol (bp)
Product	Castrol Radicool Si-OAT
Part numbers (as published)	not published
Sizes (as published)	not published
Chemistry	Si-OAT
Base glycol	not published
Colour	not published
Premix or concentrate	Concentrate
OEM / industry specs listed	MAN 324 Typ Si-OAT, MB 325.5, VW TL 774-G, JIS K2234, BS 6580
ASTM standards listed	ASTM D3306, ASTM D4985
Service life claim	protects for up to 3 years
Freeze point (as published)	-18°C
Free-of claims	nitrite-free, phosphate-free, amine-free
Datasheet	not published
Source	manufacturer page
Last checked	22 October 2026

Specs and approvals listed by the manufacturer

Meets MAN 324 Typ Si-OAT per Antifreeze is glycol plus inhibitors. Choose it by your vehicle's specification. (MAN)
Meets MB 325.5 per Antifreeze is glycol plus inhibitors. Choose it by your vehicle's specification. (Mercedes-Benz)
Meets VW TL 774-G per Antifreeze is glycol plus inhibitors. Choose it by your vehicle's specification. (Volkswagen Group)
Meets JIS K2234 per Antifreeze is glycol plus inhibitors. Choose it by your vehicle's specification. (Japan (JIS))
Meets BS 6580 per Antifreeze is glycol plus inhibitors. Choose it by your vehicle's specification. (British Standard)
Meets ASTM D3306 per Castrol (industry test standard)
Meets ASTM D4985 per Castrol (industry test standard)

Manufacturer wording: Product Performance Claims (Castrol PDS, 07 Apr 2022): ASTM D3306 (I), ASTM D4985, BS6580:2010, JASO JIS K2234, MAN 324 Type Si-OAT, MB-Approval 325.5, VW TL-774G (G12++). The PDS adds that it is compatible with older TL 774-C and TL 774-F fluids and can be used where TL 774-J is recommended.

"Meets X per manufacturer" is our shorthand for any of the manufacturer's own phrases: meets, meets or exceeds, approved, or recommended for applications requiring. It is the manufacturer's claim, not an approval by Coolant.com or by the vehicle maker. Codes are copied as published. Some sources list codes for compatibility rather than formal approval. The wording above shows which.

What the manufacturer says it is for

Castrol Radicool Si-OAT is approved for use in VW vehicles requiring VW TL-774G (G12++) approval .

Quoted from the manufacturer's page. Coolant.com has not verified fitment for any vehicle, and a listed make or year range is the manufacturer's statement, not ours.

Compatibility notes

If your owner's manual calls for MAN 324 Typ Si-OAT, Castrol lists that code for this product. Read the exact wording above, and confirm against your manual.
Chemistry is listed as Si-OAT. Mixing different chemistries can shorten coolant life. See OAT vs HOAT vs IAT and use the mixing checker before topping up.
Sold as a concentrate: dilute with distilled or deionised water as the label directs. See premix vs concentrate and the freeze and boil calculator.

Note: Castrol product data sheet, hosted by a New Zealand distributor (ILS). Life claim per data sheet.

Always check your owner's manual first. Use the coolant spec printed in your owner's manual or service information. A listing here is the manufacturer's own claim (meets, exceeds, approved or recommended, worded as they put it). It is not our approval and not a fitment guarantee for your vehicle. If in doubt, ask your dealer or a qualified mechanic.

Where to buy

We did not find a retailer link on the manufacturer's page that we could check. Try the manufacturer's own site: Castrol product page.

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Browse the full coolant directory, or use Find my car coolant to match the spec in your owner's manual.

Sources

Castrol product page (status on 22 Oct 2026: 200)

Castrol Radicool Si-OAT: specs and approvals