Antifreeze
5 Answers
Your Cadillac probably has the red Dex-Cool in it. Top it off with a 50/50 mix of red Dex-Cool and distilled water or buy some that is premixed 50/50. Green can cause issues such as cooling system deposits and break down of the antifreeze.
Do I have to drain completely and then put in fresh red mixed 50/50 with distilled water
That is up for debate. It may depend on how much green stuff you put in. The Dex-Cool is good for 5 years so if the coolant hasn't been changed in a few years I would do a coolant flush and replace the antifreeze.
You can use green just dont mix with DeX cool. I drain all and use long life antifreeze. No issues been 10+ years now. Just like premium fuel I use regular and put a bottle of octane booster into my tank then fill. Sine 50,000 miles now has 143456 no issues. Just dont add a huge bottle or it can cause problems if you add too much you'll know you will smell it not burning. I use the small orange bottle. Stoops octane booster I think.