Advice needed-Coolant amount

Read the instructions on the product's container. It likely will give different mixes for different expected low temperatures.

Make sure you are using a coolant compatible with your car. I don't think it was a problem in 1990, but it is today with some cars.

50-50 will get you to -34*F. If you need lower than that then move south because it's just too cold for any living body.

Unless it is pre-mixed. :-)

There are so many new formula stuff out there, I am not sure that the old 50:50 mix is still correct for all of them. You may know, but I offer this warning in the event you had not considered that. That is why I suggested consulting the information on the original container.

Correct, always pays to READ the container of what ever stuff one uses. But then again I would like to see more read the cars owners manual.

I would be happy if more of them even knew they had a manual.

Yep. Time to move down to Mayorca...