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.
What to buy
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Where to buyConfirm the specification in your owner’s manual before buying. Product examples are not a fitment guarantee.
Specifications
| Brand | Castrol |
|---|---|
| Maker | Castrol (bp) |
| Product | Castrol Radicool Si-OAT |
| Chemistry | Si-OAT |
| 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 |
| Not published by the maker | Part numbers, Sizes, Base glycol, Colour, Datasheet. Check the product label or ask the manufacturer. |
| Source | manufacturer page |
| Last checked | 22 October 2026 |
Specs and approvals listed by the manufacturer
- Meets MAN 324 Typ Si-OAT per Castrol (MAN)
- Meets MB 325.5 per Castrol (Mercedes-Benz)
- Meets VW TL 774-G per Castrol (Volkswagen Group)
- Meets JIS K2234 per Castrol (Japan (JIS))
- Meets BS 6580 per Castrol (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.
Alternatives that list the same spec
Other coolants whose makers list at least one of the same OEM codes as Castrol Radicool Si-OAT. More shared codes first. Match the exact code in your manual, and do not mix chemistries when topping up.
| Product | Same code(s) |
|---|---|
| Shell Coolant Longlife Plus Concentrate Shell · Si-OAT · Concentrate | MAN 324 Typ Si-OAT, MB 325.5, VW TL 774-G |
| Zerex G40 Antifreeze Coolant Zerex · not published · Concentrate | MAN 324 Typ Si-OAT, MB 325.5, VW TL 774-G |
| Xstream G40 Antifreeze & Coolant Concentrate Comma · Si-OAT · Concentrate | MAN 324 Typ Si-OAT, VW TL 774-G |
| Shell Coolant Longlife Plus Ready to Use Shell · Si-OAT · Premix (ready to use) | MAN 324 Typ Si-OAT, VW TL 774-G |
| Xstream G40 Antifreeze & Coolant Ready Mixed Comma · Si-OAT · Premix 50/50 | MAN 324 Typ Si-OAT, VW TL 774-G |
| OEM Extended Life EURO I Antifreeze/Coolant Recochem · HOAT · Concentrate and Premix 50/50 | VW TL 774-G |
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.
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.
Related tool
Compare this coolant side by side
Open the comparison →Related products with the same listed chemistry
Related products with the same listed chemistry
- Shell Coolant Longlife Plus Concentrate (Shell, Concentrate)
- Shell Coolant Longlife Plus Ready to Use (Shell, Premix (ready to use))
- Xstream G40 Antifreeze & Coolant Concentrate (Comma, Concentrate)
- Xstream G40 Antifreeze & Coolant Ready Mixed (Comma, Premix 50/50)
- Mobil Antifreeze Ultra (Concentrate) (Mobil, Concentrate)
- PEAK ORIGINAL EQUIPMENT TECHNOLOGY Antifreeze + Coolant 50/50 Prediluted for European Vehicles - VIOLET Check price (PEAK, Premix 50/50)
Vehicle makes linked to this coolant
These make pages explain what each vehicle maker specifies. The reason each one links here is shown next to it. This is not a fitment claim, so check your owner's manual.
- What coolant Volkswagen specifies (the manufacturer lists a spec code from this vehicle maker)
- What coolant Audi specifies (the manufacturer lists a spec code from this vehicle maker)
- What coolant Mercedes-Benz specifies (the manufacturer lists a spec code from this vehicle maker)
More from Castrol
See every Castrol product we list, with the chemistries and spec codes the maker names, on the Castrol coolant brand page.
See all Castrol coolants, coolants by brand or coolant by car make.
Browse the full coolant directory, or use Find my car coolant to match the spec in your owner's manual.
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