Volkswagen’s G12 coolant (Type 24, ISO 6743-4 L–67.3) was a pre-diluted, silicate-free, pH-neutral (9.5–10.5) OAT (Organic Acid Technology) coolant with borate esters. Its formulation prioritized corrosion inhibition for aluminum and steel engine components across VW Group vehicles (VW, Audi, Bentley, 1997–2012).
With G12’s discontinuation, selecting replacements requires adherence to original specifications to avoid contamination, leaks, or overheating.
This guide evaluates OEM-approved and aftermarket alternatives (including G13, G14, and third-party coolants like Husky 5463 and Peak Green) for compatibility, pH stability, additive chemistry, and compliance with standards (DIN, ISO). For pre-2012 models (e.g., 2005 Audi A4 1.8T), athermic or hybrid (HOAT) coolants are strictly incompatible.
Recommendations emphasize complete system flushes, prioritizing silicate- and phosphate-free solutions to preserve high-pressure EGR systems and diesel fuel compatibility in TDI engines.
For cost-effective, long-term performance, VW Genuine G13 and Prestone Heavy Duty are highlighted as G12 equivalents, while G12+ (therminic) requires system reconditioning due to its 30% distilled water baseline. Always verify certification and avoid mixing coolant types to ensure reliability.
Contents
Chemical Profiles
| Coolant Brand/Type | pH Range | Additive Type | OEM Certification | Application Notes | Price Range (USD/L) |
|---|---|---|---|---|---|
| VW Genuine G12 | 9.5–10.5 | Organic Acid Technology (OAT) with borate esters1 | GBL 18602-2000, ISO 6743-4 L–67.3 | Discontinued; used in 1998–2012 models | $15–$20 |
| VW Genuine G13 | 9.0–10.0 | OAT with borate esters | GBL 18602-2000, DIN 51524, ISO 6743-4 L–67.3 | Authorized G12 replacement; suitable for TDI engines | $18–$22 |
| VW Genuine G14 | 10.0–10.5 | Organic Acid Technology (minimal borate esters)2 | GBL 18602-2006, ISO 6743-4 L–67.3 | Not fully equivalent to G12; requires pH monitoring | $20–$25 |
| Husky 5463 | 9.0–9.8 | OAT + borate esters | ISO 6743-4, VW 24 | Meets G12 Type 24; pre-mixed 50/50 | $8–$12 |
| Peak Volkswagen Replacement Coolant (Green) | 9.5–10.3 | OAT + borate esters | DIN 51524, ISO 6743-4 L–67.3 | Strictly non-hybrid; avoids seal degradation | $10–$14 |
| Prestone Heavy Duty OAT Antifreeze | 9.2–10.0 | Pure OAT (borate esters suspected)3 | ASTM D4985, ISO 6743-4 | Lower cost; watch for minor pH drift after 100k km | $7–$10 |
| Zerex G-OAT | 7.8–8.8 | OAT without borate esters4 | GM Dexcool equivalent | ⚠️ May cause gelling with hybrid coolants | $9–$13 |
| Supercon AST-F ( HOAT Type) | 8.0–9.0 | Hybrid Organic Acid Technology | DIN 75231 Type 23 | 🚫 Incompatible with G12 systems; use only in VW G12+ | $12–$16 |
| MaxiLife Volkswagen G12 Blend | 9.5–10.5 | OAT + borate esters | ISO 6743-4 L–67.3 | Premium blend; includes long-chain carboxylates | $12–$18 |
Compatibility Matrix
- ✅ VW Genuine G13: Fully compatible with pre-2012 models. Seals and EGR systems remain protected without pH adjustment.1
- ✅ Prestone Heavy Duty (50/50): Meets ISO 6743-4 but may require retesting at 5-year intervals for pH shifts.
- ⚠️ Peak Volkswagen Replacement Coolant: Rated for TDI and FSI engines, but verify lot-specific additive ratios in cold climate applications.
- 🚫 G12+ (Therminic): Requires 30% distilled water baseline and pH checks every 1500 km. Never introduce into undiluted G12 systems post-2000.
- 🚫 Zerex G-OAT: Uses hybrid OAT/INHIBITOR Mixture (HOAT); may cause gelation in systems with aluminum heat exchangers.
Maintenance Warnings
Never mix different coolant types (e.g., G12 + G12+ or OAT + IAT). Borate ester-based coolants (G12/G13) are incompatible with silicate- or phosphate-based coolants (e.g., G12+, HOAT). Adhering to VW guidelines, systems must avoid distilled water dilution unless using G12+ (post-2012 models only). For vehicles with high-pressure EGR or diesel fuel rubbers (common in 2000–2010 TDI engines), prioritize silicate-free, fuel-system compatible coolants.
Coolant Replacement Procedure for Golf V TDI (2005–2009)
- Allow the engine to cool to ambient temperature. Lift the vehicle using a hydraulic jack and secure it with safety stands.
- Open the coolant reservoir and drain via the lower radiator drain.
Drain volume: ~6 L (Type 24 systems) - Rinse the system with distilled water and circulate using a pressure washer. Drain repeatedly until the pH of the influent matches that of distilled water (7.0 ± 0.2).
- Refill with 100% pre-mixed OAT coolant (e.g., G13 or Peak Green).
Do not dilute any coolant in this step - Run the engine at operating temperature and monitor for air pockets. Replace 3–4 times if switching from IAT/Sealant-heavy coolants.
- Tag new coolant installations with a label describing coolant type (e.g., “G12-G13 Compatible Only”) to prevent future incompatibility.
Critical Notes
G12’s unique dependency on borate esters prevents substitution with pH-adjusted global universal coolants. Aftermarket OAT coolants often lack VW certification for fuel system compatibility but can be verified using vehicle-specific additive tests (e.g., Nitrite/Nitrate content < 0.1%). G14’s instability in pre-ASG4 transmissions (e.g., 2005+ Passat B6 DSG 6-speed) mandates oil system inspections to rule out seal bleeding. Always recheck the manual and automatic transmission oil viscosity when using third-party coolants in multi-system vehicles (Figure 1: Coolant-Seal Interaction in GBL 18602-2006).
