Quick answer
G11, G12, G13 and G48 coolant explained: "G" names are European coolant designations that describe a formulation family. Broadly: G11 = silicated hybrid, G12/G12+ = OAT (organic acid, silicate-free), G12++/G13 = Si-OAT (organic acid plus silicate), G48 = silicated hybrid. They aren't universal standards, so always match the exact spec number in your owner's manual.
Key takeaways
- G-names are trade designations, not international standards.
- G11/G48: silicate-containing hybrids. G12/G12+: OAT. G12++/G13: Si-OAT.
- Products labelled "G12" by different makers can differ in formulation.
- Match the OEM spec number in your manual, not just the G-name.
- Don't mix G-types unless the vehicle maker allows it. When unsure, drain and refill.
G-designations at a glance
| Designation | Commonly described as | Notes |
|---|---|---|
| G11 | Silicated hybrid (older) | Common in older European vehicles |
| G12 / G12+ | OAT (silicate-free organic acid) | Long-life; "+" versions were developed for improved compatibility |
| G12++ / G12evo | Si-OAT (organic acid plus silicate) | Later evolutions; check the exact spec |
| G13 | Si-OAT, glycerin-containing formulation | Later evolution |
| G40 | Si-OAT family | Name used by some suppliers |
| G48 | Silicated hybrid (HOAT) | Used by several European makers |
| G05 | Hybrid (low silicate) | Name used by some suppliers |
These are general descriptions used across the aftermarket. Formulations vary between suppliers, and vehicle makers publish their own spec numbers. Your manual is the authority.
Why the exact spec number matters
A bottle saying "G12" tells you the family, but each vehicle maker has its own specification number that coolants are tested and approved against. Coolant makers then print which specs their product meets or is approved for. Two "G12" products can have different approvals. When you buy, look for your manual's spec number on the label, as described in what coolant does my car need?.
G11 vs G12: what's the difference?
G11 contains silicate (a hybrid), while G12 is silicate-free organic acid (OAT). They protect metal by different mechanisms. Mixing them dilutes both packages, and some sources report that certain combinations can form deposits. If your car has G11 and you need G12 (or the reverse), the safe approach is a full flush and refill to the specified type. Check combinations below.
Coolant mixing checker
G12 vs G13: can you mix them?
G13 and G12++ are later Si-OAT evolutions. Some vehicle makers describe later grades as backward-compatible with certain earlier ones, but rules differ by maker and spec. Follow your manual or the carmaker's service information. If that isn't available, don't mix. Use the specified coolant, or drain and refill.
What is G48 coolant?
G48 is generally described as a silicate-containing hybrid (HOAT-type) coolant and is used by several European vehicle makers. As with every G-name, check that the label lists the spec your manual requires.
Premix or concentrate?
Most G-types are sold both ways. Concentrate is diluted, typically with distilled or deionized water, to the ratio on the label; 50/50 is common. Some ready-mixed G13 and G12 products are sold at other ratios, such as 40/60. See premix vs concentrate.
Common mistakes
- Treating G-names as standards. They are family names, so check the spec number.
- Mixing G11 with G12. Different chemistries. Flush and refill instead.
- Choosing by color (pink, purple, blue). G-type colors vary by supplier.
- Topping up with "universal". Only if its label lists your spec.
Buying a G-spec coolant: what to look for
- Label lists your manual's exact spec number or approval
- Premix or concentrate as needed
- Correct volume for a top-up or full refill
Specific product recommendations are not published yet. We only list products we have checked against published specs.
Reading VW/Audi-style spec names
Coolant names such as G12, G12+, G12++, G13 and G48 are commonly used to describe specific European coolant families. Bottles in the aftermarket may say "meets G13" or "suitable for TL 774-J". Specifications can be revised over time, so check that the product matches the exact spec your vehicle lists, not just the family name. If you're unsure, a dealer parts department can confirm the spec for your VIN.
G48 and similar silicate coolants
Silicate-containing hybrid coolants, often associated with the G48 name, are used by some European carmakers. They are a different family from the organic-acid G12-type coolants. Mixing them is generally not recommended. Use the type specified for your vehicle.
About to top up with a different coolant?
Check compatibility →Topping up a European car on the road
- Check the reservoir cap or manual for the spec.
- Buy a premix that names the spec, if available.
- If not, use distilled water to get home safely.
- Restore the correct coolant soon and record it.
Common mistake
- Buying "G12" for a G13 car because the color looks similar. Specs differ. Match exactly.
More questions answered
Can G13 replace G12?
Often yes where the carmaker permits it. Check the official guidance.
Is purple coolant always G13?
No. Color isn't a spec.
Reader questions
Where's the spec printed?
Often on the reservoir cap or label, and in the manual.
Is G12 still sold?
Availability varies. Use the spec your car lists.
Key point to remember
Exact spec matching is what matters with European coolant families.
In practice
In practice, European dealers and parts counters can confirm the exact coolant spec for your VIN in seconds. Note it in your service records. If you buy aftermarket, check that the bottle states the spec number, not just "for VW/Audi".
Next step
Ask a dealer for your VIN's spec.
One more tip
Keep the spec in your phone.
When to see a mechanic
See a mechanic promptly if…
- you've mixed G-types and see deposits or gel
- you have overheating or coolant loss
- you need a full flush to change type
Specs referenced: ASTM D3306 (glycol-base engine coolant for automobile and light-duty service) and ASTM D6210 (fully formulated glycol-base coolant for heavy-duty engines). Your owner's manual and the OEM spec number take priority.
Frequently asked questions
Is G12 the same as G13?
No. Both are organic-acid families, but G13 is a later Si-OAT formulation. Use the one your manual specifies.
Can I mix G11 and G12?
It's not recommended. They use different inhibitor chemistry. Drain and refill with the specified coolant instead.
What type is G48 coolant?
G48 is generally described as a silicate-containing hybrid (HOAT) coolant. Match the exact spec in your manual.
What does the plus in G12+ mean?
It marks a later G12 formulation. Check the label's spec approvals rather than relying on the name.
New to cooling systems? Start with how a car cooling system works. Looking for a product? Search the coolant directory or match your manual's spec with Find my car coolant. See also coolant by car make and coolants by brand.