I use this in my Roadster without issue - click for source.
![[Linked Image]](https://i.ebayimg.com/images/g/NiYAAOSwARZhu2O7/s-l400.jpg)
It can be used neat as I did since old coolant was found to have same -40°C protection although this allows for some dilution if required.
Not familiar with +8 but typically there should be some coolant remaining in expansion tank after engine cools.