Coolant G11, G12 or G13: what differs and what to use
In short
G11 is a silicate-based coolant with a typical life of 2–3 years; G12 and G12+ use organic acid technology and last around 5 years; G12++ and G13 are hybrid formulations, with part of the base replaced by glycerine in G13, again around 5 years or as the manual states. Colour is not a specification, the classes must not be mixed, and the usual ratio of 50% concentrate to 50% demineralised water gives protection to roughly −36 °C.
What coolant does beyond freeze protection
The common name is misleading, because freeze protection is only one of the coolant's jobs, and far from the one it performs most often through the year. First, it raises the boiling point. A correct mixture in a pressurised system copes well beyond 100 °C, which prevents vapour bubbles forming in the hot regions of the cylinder head. A vapour bubble means no contact with the metal and a local hot spot. Second, it protects against corrosion. A cooling system contains aluminium, cast iron, brass, copper, solder joints and rubber seals, all in permanent contact with a hot liquid. Without inhibitors, aluminium corrodes quickly, and the corrosion products block the radiator and the heater matrix. Third, it lubricates the water pump seal and limits cavitation — the tiny bubble implosions that literally erode pump impellers and cylinder liner walls. That is why plain water, even in summer, is not an acceptable alternative.
G11, G12 and G13: the chemical difference
The names G11, G12 and G13 come from one large European manufacturer's nomenclature and have entered everyday use, even though every carmaker has its own specifications. G11 belongs to inorganic chemistry, based on silicates. The inhibitors form a thin protective layer over every metal surface in the system. That is effective and fast-acting, and it protects the copper and brass in older radiators well, but the layer depletes over time and silicates can drop out of solution. Hence the shorter service life. G12 and G12+ use organic acid technology, based on carboxylates. The inhibitors do not coat everything; they act only where corrosion begins. They deplete more slowly, which extends the service life, and heat transfer is marginally better because there is no deposited layer. In exchange, they suit older systems with a lot of brass and solder less well. G12++ and G13 are hybrid formulations combining an organic base with a small mineral component, and in G13 part of the ethylene glycol base is replaced by less toxic glycerine. Performance remains similar to the organic versions.
Why the classes must not be mixed
This is where the real consequences appear. When a silicate coolant meets an organic acid one, the additives can react: silicates come out of solution and the mixture forms a gel or a fine whitish deposit. The result is not immediately visible. It shows up later as a heater matrix that no longer warms the cabin, temperature climbing in traffic, blocked cells in the main radiator and premature wear of the water pump seal. Those symptoms take months to appear, by which point almost nobody connects them to a top-up made at some point on the road. Colour will not save you from the mistake. There is no standard linking a colour to a chemistry: blue, green, red, pink, violet and yellow are commercial choices. Two red liquids can belong to different chemical families. The safe rule is to top up with exactly the same product. If you do not know what is in the system, or if a mixture has already happened, the correct route is to flush the system and refill with the class the manual requires. In a genuine roadside emergency, demineralised water is a less harmful top-up than a coolant of unknown class, provided you correct the mixture as soon as possible.
The correct dilution ratio
Concentrate is never poured in neat. Pure ethylene glycol has, paradoxically, a higher freezing point than a mixture with water, and it also transfers heat less effectively. The usual ratios are simple: 50% concentrate with 50% demineralised water protects to roughly −36 °C, while 60% concentrate with 40% water pushes protection towards −50 °C. Above roughly 65–70% concentrate, freeze protection starts getting worse rather than better. The water matters more than people expect. Tap water contains calcium, magnesium and chlorides, which form deposits on hot surfaces and accelerate aluminium corrosion. Use demineralised or distilled water. Pay attention to ready-mixed products, labelled ready-mix or −36 °C: those are poured in as they come. Diluting them further with water destroys exactly the protection you paid for. Check the label before opening the container, because the two versions look very similar on the shelf.
Service life and how to check condition
As a general guide, silicate coolants are changed every 2–3 years, while organic and hybrid types last around 5 years or as long as the car's manual states, which always takes priority. Some cars quote much longer intervals for the factory fill. The practical check uses a refractometer or a coolant hydrometer, both inexpensive and available in any serious workshop. The measurement takes a minute and tells you the exact temperature at which the mixture in your car will freeze — something no colour can reveal. Signs that the fluid needs replacing: a colour that has turned brown-rusty or cloudy, particles floating in the tank, deposits around the filler neck, a changed smell. A clear, brightly coloured liquid is generally a good sign. Check the level with the engine cold, between the MIN and MAX marks on the expansion tank. Never open the cap on a hot engine: the system is pressurised and hot coolant can spray out. Check the cap itself, which maintains working pressure, and the hoses — a cracked or soft hose is about to fail.
What this means in Moldovan conditions
Our winters drop towards −20 °C in some years, and lower still in the north of the country, while summers regularly pass 35 °C. A mixture protecting to −30 °C or better covers both extremes comfortably and leaves margin for the water top-ups made through the year. The right moment to check is autumn, before the first freezing nights, together with the battery and the washer fluid. A one-minute refractometer test is enough. An important safety note: ethylene glycol coolant is toxic to people and animals and tastes sweet. Do not leave it in open containers, clean up any spill in the yard immediately, and take used coolant to an authorised collection point rather than pouring it away. Our catalogue carries MANNOL coolant in both concentrate and ready-mixed versions, matching the classes common on European cars. If you are not sure what is currently in the system, call us on +373 22 009 350 and we will tell you what the factory specifies for your car.
Need the part we wrote about?
The catalogue carries the right products, priced in MDL with delivery across Moldova. If you are unsure about fitment, call us and we will check it against your VIN.
Frequently asked questions
Can I top up with water if the level has dropped?
In an emergency yes, preferably demineralised water and in small quantity. Water dilutes the coolant and raises the freezing point, so check the concentration with a refractometer as soon as possible and correct the mixture before winter.
Does the colour tell me the coolant class?
No. Colour is a commercial choice, not a technical standard. Two liquids of the same colour can have incompatible chemistries, so go by the class printed on the label and the requirement in your manual.
What if two different classes have already been mixed?
If it was a small top-up and no symptoms appear, watch the temperature and the fluid condition closely. The safe option remains flushing the system and refilling with the correct fluid, especially if the mixture sat for a long time or you can see gel-like deposits.
Can concentrate be poured in directly?
No. Concentrate is diluted with demineralised water, usually at 50/50. Ready-mixed products, labelled ready-mix, are poured in as they come — check the label, because the packaging looks alike.