Antifreeze choice
Q You kindly gave me advice on changing the coolant in my 2010 Nissan Pixo a couple of years ago. Due to me overlooking the previous coolant change carried out at a main dealer before I started home servicing my vehicles, I have not attempted the procedure until now. I have some further questions that I hope you are able to answer. The current coolant in the Pixo is green. I am looking at purchasing new coolant, but I would appreciate your advice on what type to choose. I have seen Prestone coolant that says it is compatible with different types of coolant and to me that seems a safe bet. I have read that different coolant colours should not be mixed (as you mention, pockets of old coolant will be left in the system during the change), but others have said that the colours don’t really matter as long as they are the same type. As I don’t know what type is in there already then that does not really help!
My other question concerns what I need to do with the expansion tank (shown in the photo). My thoughts are to empty the expansion tank once I’ve drained the system down, and then refill once I have topped with new coolant through the radiator cap
– or should I only refill once the engine is up to temperature and I have replaced the radiator cap?
Trevor Nicholson A The coolant which should be in your Pixo is an ethylene glycol-based antifreeze with OAT (Organic Additive Technology) inhibitors. The colour of any antifreeze is only used as an identifier and as different manufacturers have used different colours this can be misleading. But mixing the colour in itself is not a problem, it is the different types of antifreeze which should not be mixed, i.e. OAT and IAT (Inorganic Acid Technology).
This is because the two coolants work in a different way, and the modern
OAT should not be used in older vehicles which may have yellow metal components in the cooling system such as brass.
Here’s a quick rundown of the different colours which have been used: Green = IAT, Orange = OAT, Yellow = HOAT (hybrid version of OAT), Turquoise = phosphatefree version of HOAT, Pink or Blue = P-HOAT (HOAT with phosphates) and Purple = SI-OAT (OAT with silicates). So as you can see things become complex.
Comma Xstream® G30® Antifreeze, or the Prestone coolant you have seen would both be suitable for your Pixo and as you intend to drain down and flush the coolant, the small pockets which remain in the cooling system will not have an adverse effect.
As the expansion tank on your Pixo is not part of the pressurised system it can be drained and topped up at any stage in the process. It should be filled with a 50/50 coolant mix.