Fuel Additive

[Sconnors]

Looking for some advice for my 1968 Cadillac as far as fuel goes, what do you guys use for octane and do you use any fuel additive??

[Dan LeBlanc]

No additive in my 1970 472 but always use the highest octane rating I can find.  Luckily, here in Atlantic Canada, premium unleaded is ethanol free.

[jdemerson]

I'd have a strong preference for ethanol-free fuel. Here in New England that means at least 91 octane, and I am pretty sure your '68 needs that (or higher). I'm not big on gasoline additives, except for Sta-Bil when storing the car and a lead substitute for cars before around 1971.

John Emerson
1952 Cadillac SedN 6219X

[David Greenburg]

And if you don't have ethanol-free fuel, I'd recommend an additive like Marine Sta-bil to protect against ethanol damage.

[jdemerson]

And if you don't have ethanol-free fuel, I'd recommend an additive like Marine Sta-bil to protect against ethanol damage.

Very much agree, and I always use the Marine version of Sta-Bil. It costs a bit more for the bottle than regular Sta-Bil, but is cheaper on a per-treatment basis (and better) in the long run. I think it's an excellent product.

John Emerson

[chrisntam]

I spoke with a Sta-bil rep at the last Mecum Auction I attended, he recommended the Sta-bil 360.  My '70 stays parked in the garage, I start it and drive it every week or two, approx. 10 to 20 miles each weekend.

I fill up every other month or so.

What is the benefit of Marine Sta-bil over the regular Sta-bil?

[James Landi]

Owning several boats powered by big block GM motors (454cid), I can attest to the harsh reality of ethanol separation--- the nasty powdery  gunk floats to the bottom of you carb, and a strata of nasty liquid that does not burn (comprised mainly of water?) can live at the bottom of your fuel tank.  The marine additive appears to work, yet better still is purchasing ethanol free fuel, especially at the end of the driving season.   Another additive that works to helps to
raise the boiling temperature in your carburetor is Marvel Mystery oil.  I add 8 oz to a full tank, and the hard starting on hot days "mysteriously" vanishes.    Happy day,  James

[The Tassie Devil(le)]

Thanks James,

That would account for the gunk that was fouling the tank, Carby and fuel pump in my boat.   I could never figure out what it was when I stripped my boat down, as having never seen the contamination before (I am a shipwright by trade) in any boat I have worked on here in Tasmania.

Sadly, it is not a Cadillac, but what I would call the Cadillac of pleasure boats.

Bruce.