‘Don’t mix the two types, doing so may cause the corrosion inhibitors to crystallise out’
BEFORE THE REALLY cold weather, it’s time to think about the engine and any wet central heating antifreeze. Antifreeze life relates to the way the anti-corrosion additives get ‘used up’ as they do their job. Older, typically blue, antifreezes might have a two-year life while modern ones (any colour, often red) may have five or ten years’ life. Don’t mix the two types: doing so may cause the corrosion inhibitors to crystallise out. Also, make sure the type you use states clearly that it is suitable for any engine.
Do not exceed a 50 percent mixture and stay above about 25 percent. I start with 50 and top up with water, so over the life of the antifreeze, the percentage gradually reduces. You can get a hydrometer to test the mixture but make sure it is calibrated for your type of antifreeze. When changing antifreeze, flush several changes of water through the system, and check and change any hoses that are perished, extra soft or extra hard.