Fuel recommendations for 1955 Eldorado 331 CI.

[Toddunger]

Greetings again.
I'm hoping to visit Sedona in a few months and take Dads Eldorado for a spin.  I'm wondering what fuel, (and additives, if necessary) I should use.  I've researched all over and it's hard to choose the best option from the wide variety of comments I have discovered.  Sadly, I don't have the service history on this car, so I don't know if the valve train has been updated for unleaded fuel.

Any ideas?

[35-709]

If by "updated for unleaded fuel" you mean hardened valve seats, it has been pretty well established for quite some time that unless the engine is used for racing or marine service where it is under a constant heavy load, hardened valve seats are not necessary.  Same with "snake oils" --- I mean additives. 

The best gasoline, more or less readily available today, to use is 89-90 octane ethanol free gasoline, sometimes called "boat gas", available at marinas and (at least here in Florida) at an ever increasing number of gas stations.  There are several gas stations here in my town that now carry it, yes, it is more expensive.

If the car sits a lot with ethanol laced fuel in it you should absolutely use a preservative such as STA-BIL, added just before you fill the tank.  Actually, it wouldn't hurt to use it with non-ethanol fuel either for a car that sits idle a lot.

Otherwise, if you can only find ethanol laced fuel, use mid-grade or Premium.

[carguyblack]

Following up on the ethanol gas comment, I would highly recommend burning non-ethanol gas if you can find it. My experience is that I wrecked my accelerator pump and fuel pump diaphragm rubber due to ethanol gas deterioration. A the least, put non-ethanol in an empty tank to run through the system prior to any lengthy storage. Good for the peace of mind to know your rubber isn't being deteriorated while the car sits.
Chuck

[Carl Fielding]

Do you guys know the compression ratio on these 55 Eldos ? Also , I think Sedona is at about the same elevation as "The Mile High City".  - Carl

[David Greenburg]

Certainly use an ethanol treatment if no ethanol free gas is available.  There is no E-0 available here in N. Cailif.  I use Marine Sta-bil or Lucas ethanol treatment at every fill up. You might also want to keep some octane booster on hand.  My '61 does not like certain hills without it.