Opel and Vauxhall Coolant Type: OAT, Dex-Cool, and Why Colour Alone Is Not Enough

BySerge Barrett

Opel and Vauxhall owner’s manuals typically say “use only Vauxhall long life antifreeze” — which is not particularly helpful when standing in front of a shelf of options. The actual specification is an ethylene glycol-based OAT (Organic Acid Technology) coolant, silicate-free, red or pink in colour when purchased as genuine product. However, since not all red or pink coolants are OAT-based, and since mixing the wrong type with existing coolant turns the system into sludge, understanding the specification rather than the colour is the correct starting point.

The Standard Specification — OAT Silicate-Free

All current Opel and Vauxhall models — Astra, Corsa, Insignia, Mokka, Grandland, Crossland, Combo, and Zafira — use an ethylene glycol-based OAT coolant meeting the following requirements:

  • Silicate-free, phosphate-free, nitrite-free, and amine-free
  • OAT (Organic Acid Technology) or MEG OAT formulation
  • Ethylene glycol base — not propylene glycol
  • Red, pink, or orange in colour when purchased as Vauxhall/Opel genuine product

The genuine Vauxhall Long Life Coolant is Dex-Cool compatible and marketed as pink/red in colour. Vauxhall’s genuine long life coolant is Dex-Cool type, pink or red in colour, and requires a 50/50 mix with water for freeze protection to −38°C. Aftermarket alternatives that meet this specification include Comma Xstream G30, Prestone OAT, and Glysantin G30.

Do not use green IAT (Inorganic Additive Technology) coolant. Vauxhall recommends an ethylene glycol-based silicate-free antifreeze (MEG OAT), which can be red, orange, or pink — not all red or orange antifreezes will be an ethylene glycol-based silicate-free OAT type, so the specification matters more than the colour.

G12+ vs G30 vs OAT — What the Codes Mean

For Corsa models from 2013 onward, OAT (Organic Acid Technology) antifreeze is required. G12+ is an acceptable product for these vehicles. The naming can be confusing, so here is what the codes mean for Opel/Vauxhall:

  • G12+ — HOAT (Hybrid OAT) with some silicate content. Compatible with most Opel/Vauxhall models up to approximately 2010. Red in colour.
  • G12++ — Low-silicate HOAT, transitional specification. Also acceptable across most models.
  • G30 — Full OAT, silicate-free. The current preferred specification for all modern Opel/Vauxhall models from 2010 onward. Red or pink.
  • Dex-Cool — GM’s OAT specification, identical in chemistry to G30. Acceptable across all current models since Opel shares its parent company with GM.

Do not mix G12+ and G30 without flushing — while both are compatible in emergency situations, mixing two different coolant types can turn the system to sludge, and incorrect coolant can damage parts of the engine.

Capacities by Model

  • Corsa E and F (1.2T, 1.4T, 1.5T diesel) — approximately 5.5–6.5 litres
  • Astra J and K (1.4T, 1.6T petrol or diesel) — approximately 6.5–7.5 litres
  • Insignia B (1.5T, 2.0T) — approximately 7.5–8.5 litres
  • Mokka and Crossland (1.2T) — approximately 5.5–6.5 litres
  • Grandland X (1.5 diesel, 1.6T petrol) — approximately 6.0–7.0 litres

Mixing Ratio and Change Intervals

A 50/50 mix of coolant to distilled or deionised water is recommended, providing antifreeze protection to approximately −28°C at this ratio. Use distilled water rather than tap water — mineral content in tap water reacts with the OAT inhibitor package and forms deposits inside coolant passages over time.

Change intervals for Opel/Vauxhall models:

  • G30 / Dex-Cool OAT — every 5 years or 150,000 miles under normal conditions. Five-year coolant is generally more cost-effective than the standard 2-year product and is the correct choice for current models.
  • G12+ HOAT (older models) — every 2–3 years depending on the formulation. Check the product label for the stated service life.

If the coolant in the reservoir appears brown, contains visible particles, or shows a rusty tinge, replace it immediately regardless of the interval. These signs indicate inhibitor depletion or early internal corrosion, both of which require flushing before they reach the water pump or head gasket.

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