Is mixing different coolants REALLY bad?

[OldSkodaDriver]

I just topped up my Skoda with coolant: BLUECOL'u' clear.
It said:
'Universal top-up antifreeze & coolant'
'All makes - All Models'
'Will mx safely with all colours of antifreeze'

Then I dug out the manual which states:
'The same coolant (G12) (red in colour) MUST always be used for topping up.'
'Mixing different coolants can result in damage to the engine'
'Have the coolant replaced immediately'

Is this true?
Thanks.

2002
Skoda
Fabia
1.4
40,000 miles

[OldSkodaDriver]

Thanks for all your replies:

Here is the reply I got (very quickly) from the manufacturer:

'Bluecol ‘U’ has been tested with coolants such the G12 type and is fully compatible to use with this product therefore you should have no worries regarding the formation of any deposits that would cause problems in the cooling system.


Regards,


Shazad Shah



ETA

Sorry but signatures are not allowed.

Edited by Big Al. on Monday 10th October 19:16