Gas additive recommendations

[Daniela]

What is the best gas additive to use? 
It’s time to get my first gas fill up and I was wondering what the best additives are (my dad is a collector in Germany and therefore I can‘t really ask him - he just told me I need an additive. lol)

[Daniela]

Yes, those already sound expensive and I wouldn’t think that I would find one easily doing road trips.
My dad is using additives for his car to make up for today’s gas being unleaded compared to being leaded in the past.

[Daniela]

Thank you!

[Daniela]

Hi Tony,
Thanks a lot for the explanation - I really appreciate it.
Guess I really need to find that mechanic and see if he can find out about the valve guides. I only know that the previous owner only used the racing gas to fill it up.

My dad has no Cadillac in his collection but he always wanted one and was indeed the one having suggested I buy this one. He is super excited to come visit as soon as it is possible again to take it for a spin. lol
He has a couple of old Jaguars, Mercedes‘, an old VW Beetle and an 1932 Packard. And all of those are his everyday cars. The most modern car my parents own is a 20yr old Smart which is scary to think might soon be old enough to be called a Classic and get a special license plate.