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)

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My 64 429 runs just fine on high octane gas at the pump — 92 octane as should a 63 390 engine 

The compression in our engines is in a range that deals well with the hight octane gas available now 

When the cars were new the octane at the pumps was 103 ( Sunoco top was 110 ) and it did add a more powerful feel to how the car performed and gas was cheep 

My own experience is the using additives gets very expensive and is a pain in the neck to do long  term keep the fuel mixture constant —but that is just me 

More octane will increase the cars power feel and will not be a problem for the engine to handle at all If you choose to go in that direction with an additive




Speed shops and Race shops ( oval racing shops ) sell high octane gasolines but again they are expensive to run on the street constantly 


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.
Thank you!

If the valve guides in the engines heads have been changed to the harder valve guides as many have over the years it is not necessary to use additives in the gasoline to add lead to it 

So the pump —-high test gas will be just fine for everyday use 

Mostly you do not want the engine to be pinging from to much timing advance  which causes high heat build up in the cylinders  and damage from anything less than 92 octane 

Does your Dad have any Cadillacs in his collection in Germany ? 

My dad had  7 Cadillacs from 62- 64 in his collection all restored registered and turn key 

The day he asked me which of the cars I would like  from his outstanding collection was a very special day in my life 

My wife says we have the car gene on both sides of our family as her dad was a car nut as well with new cars often ever 6 months and car dealerships owners  being close friends 


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.



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