Caravan and Motorhome Antifreeze: Which One and How Much

Antifreeze Guide

A practical guide from Bedam Leisure — caravan & motorhome specialists

Caravan and motorhome antifreeze goes in the heating system, not the water pipes — and on a van with an Alde wet heating circuit, that circuit usually holds between 10 and 14 litres of ready-mixed glycol. Use the grade the manufacturer specifies, Alde Premium G12 EVO or G12++, never car antifreeze, and top up cold until the expansion tank sits between its minimum and maximum marks.

Everything here is in our winterising collection and the Alde parts range.

1 Which system

Wet heating takes antifreeze. Water systems do not.

If your van has an Alde Compact 3010, 3020 or 3030, you have wet central heating: a sealed loop of glycol and water pumped round convectors or radiators, sometimes with an underfloor circuit too. It stays filled all year. The glycol is what stops it freezing, and what stops the aluminium inside the boiler corroding.

If your van has a Truma Combi, an Ultraheat, a Whale or a Propex, you have warm-air heating and a separate fresh water system. Neither takes antifreeze. Fresh water is drinking water — you protect it by emptying it, which is covered in our drain down and winterising guide.

Both at once? Plenty of Swift, Bailey, Lunar and Buccaneer vans have Alde heating and an ordinary fresh water system. Two separate jobs: glycol stays in the heating loop, the water system gets drained. Doing one and forgetting the other is the commonest autumn mistake we see.

2 Which fluid

Alde Premium G12 EVO, G12++ or G13 — and nothing else

Alde specify their own glycol for a reason: it is a silicated OAT formula matched to the aluminium, brass and rubber in their boilers. Car antifreeze has a different inhibitor package, attacks the aluminium and swells the rubber connections — the cheapest fluid you can buy and the dearest mistake you can make.

The current fluids are Premium G12 EVO and Premium G12++. Both come premixed, protect to around -37°C, are rated for up to five years of corrosion resistance, and are intermixable with each other and with Premium G13. Because they arrive premixed you never dilute them — water weakens the frost point and the inhibitors together.

3 How much

Working out what your system holds

There is no single figure, because the boiler is only part of it. The fluid is shared between the boiler, the pipe runs, the convectors and — on newer caravans — an underfloor loop, so a short two-berth might take 8 litres where a twin-axle is closer to 14. Your handbook has the exact figure — write it inside a locker door.

For topping up, forget capacity and use the expansion tank. Check it cold, not after a run with the heating on, or the fluid will have expanded and you will overfill. The level wants to sit between the minimum and maximum marks; below minimum, top up with the same grade. Never with water.

Two parts are worth a look while you are there. A crazed tank makes the level impossible to read; a perished cap loses glycol for months unnoticed.

Not the same as FrostControl. The Alde FrostControl valve protects the fresh water heater, dumping it at around +3°C. Nothing to do with the glycol circuit, and vans with both catch people out every year.

4 When to change it

Frost protection lasts. Corrosion protection does not.

This is the part people get wrong. Glycol does not stop working as antifreeze — the frost point stays roughly where it was for years. What runs out is the corrosion inhibitor package, and once that is spent the fluid quietly attacks the aluminium inside the boiler. No warning until something leaks.

Alde's older fluids ran to a two-year change interval, and plenty of vans are still on that schedule because nobody told the owner otherwise. The current Premium G12 EVO and G12++ are rated for up to five years. Check your handbook, and if you have no idea when it was last done, change it now and start the clock from a date you know.

Look at the colour while you drain: fresh Alde glycol is clear and bright, and dark or cloudy fluid has been in far too long. Bleed properly after filling — air pockets are the usual reason a radiator stays cold at one end, and they take a few heating cycles to clear, so expect to top up again a week later.

Disposal matters. Ethylene glycol is sweet-tasting and poisonous to cats, dogs and wildlife. Drain the old fluid into a sealed container and take it to a household waste recycling centre. Never tip it down a drain or onto a pitch.

5 Truma and Whale

No wet heating? This is your version of the job

Warm-air vans get their frost protection from a valve, not a fluid. On a Truma Combi that is the frost control element, which dumps the water heater when the temperature at the valve drops to about 3°C. A cheap part that decides whether a Combi survives a cold snap — and it fails closed, the wrong way round.

Touring through the cold rather than laying up? Read getting the best from Truma and Alde heating next.

Common questions

Can I use car antifreeze in an Alde system?

No. Automotive antifreeze corrodes the aluminium and swells the rubber connections in an Alde circuit. Use Alde Premium G12 EVO, G12++ or G13 only. The saving is a few pounds; a boiler is several thousand.

How much antifreeze does an Alde Compact take?

Most tourers take 10 to 14 litres for a complete change, depending on the convector run and whether underfloor heating is fitted. Your handbook gives the exact figure. For topping up, ignore capacity and fill to between the min and max marks, cold.

Do I need antifreeze in my caravan water pipes?

No — never put glycol in a drinking water system. Fresh water systems are protected by draining them down completely before the first frost, not by adding anything to them.

How often should Alde glycol be changed?

Older Alde fluids ran to a two-year interval; the current Premium G12 EVO and G12++ are rated for up to five years of corrosion protection. Check your handbook for your system, and if the change date is unknown, do it now and record it.

Can I mix G12 EVO with G12++ or G13?

Yes. Alde Premium G12 EVO, G12++ and G13 are intermixable, so top up with whichever you have. Do not mix them with automotive antifreeze and do not dilute with water — they are supplied ready to use.