Mixing coolant.

Is the coolant meant to be checked engine cold or hot? It will expand quite a lot.

There is more than one type of coolant.

Recent Fords use an OATs organic acid system for anti-corrosion. I would suggest do your research first before adding the stuff you have on the shelf.

There is anecdotal evidence not all types mix.

IOW, "not miscible in all proportions" to use the technical terminology. :)

These are certainly considered miscible, but react to form a sludge.

As opposed to oil and water that are not miscible.

Isn't miscible just a posh way of saying mixable?

They are miscible or mixscible (arrgh!) with water anyway.

The big divide is between the blue and the red coolants, only one kind should be used.

My impression is that the red coolant is the current issue for modern cars?

There is another type of posh coolant which is claimed totally permanent; that is assuming that your coolant system has no leaks.

A small leak + topping up is convenient way of renewing the coolant as the anti corrosive properties are time limited.

Possibly, except mayonnaise is mixable yet not miscible. There are other thixotropic mixes out there too.

I feel I have donned a pedantic hat!

thixotropic rust remover = Irishman with wire brush ...

(Sorry)

OAT style antifreeze is meant to last longer and is used by Ford and others. It can only be used where there are no copper alloys used. For that you need the old IAT.

A good article is here:

You're probably thinking of Hybrid Organic Acid Technology (HOAT)?

I often add a litre of concentrate every other year or so!

Same here. Never top up with water or a water/antifreeze mixture.

Thanks for nice web link. As usual life is morre complicated than you think (or care about). It's like when you are thinking of doing something, then first study all the literature, consolidate all the information and mull over it for a couple of years...

Not just me, then :-)

Topping up with a litre every 2 years seems an awful lot- even in total. I check our vehicles regularly and doubt I put in 200ml a year, if that.

They are all modern 'sealed' systems with header tanks. The older style systems were prone to loss but I'm be surprised if one lost the equivalent of 500ml / year.

As an aside, I notice that some cars (Eg my Honda) had very long life coolant originally. However, if I recall the service schedule, even if you replaced it with Honda coolant, the replacement time for later changes was far less. Purely from memory- the original coolant was good for 5 years but replacement (even Honda's) only 2.

Ford specify a 10 year antifreeze. (Up to 10 years)

TBA, the Honda may have been 10 years, I can't recall and I passed on the handbook with the car. I do recall that, even using Honda replacement, future changes were more frequent.

I suppose it is possible the original stuff could be supplied 'over the counter' for some reason.

colour of coolant varies around the world ... so beware if some webpage tells you to use red/green/blue ...