Gas grade question

I forgot to ask the previous owner which grade gas he used. I've been putting in mid grade? Suggestions please.
1960 CJ5 Fhead stock.

 

Use the lowest octane you can that does not cause the engine to knock (premature detonation). If you can run 86 or 87 Octane and the engine runs fine, do so. the only reason to run higher octane fuel is if 1) the manufacture recommends it or 2) you are experiencing engine knock. The only reason the manufacture recommends higher octane is to prevent knock on high compression engines.

 

A ’60 with a stock F-head? Run the dog water, 87 octane.
Stay away from the “gasohol”, 10% ethanol, though. Your engine would probably burn it just fine but your fuel system won’t like it pumping it all the time.

 

And good luck on staying away from gasahol, That is all the winter grade stuff is.
I just run the 87 in mine. I have had no problems with it.

Same thing with my antique goldwing.

If your vehicle sits for long periods of time without being run, the stuff rated higher than 87 turns to varnish faster and will gum up your carb quicker than the 87 will. Have no idea why, but there it is.

 

With approximately 7:1 compression ratio, it would almost run on kerosene.

 

X2. I've read and heard too many things about ethanol, its characteristics, and its affects on fuel systems. This website might help you find non-ethanol gas: www.pure-gas.org

FWIW, my sister's '84 XJ Cherokee (with the 2.5L AMC I-4) runs noticeably better on 89 than 87 octane, and while it isn't always noticeable my '85 GMC C3500 (with the 454 ) seems to run a little better, too. Dad says the '69 DJ5A runs a lot better on plus, as well.

The old F-head was probably designed to run on much lower octane fuel (my 1950 Farmall Cub says 70-something octane fuel in the operator's manual, and it'll run on 6-month old ethanol gas) so regular may be adequate for it, but my experience with older engines has been that plus helps. JM2CW

 

Yup, 68 octane is specced on my M38A1 data plate. And I remember when "regular" octane was in the low 90's.

 

"Straight run gasoline" refined directly from crude oil has an octane rating of 70. This is basically the same as camp stove fuel.

So just about anything that qualifies as gasoline should be suitable. Modern gasoline is chemically manipulated to bring the octane rating up, and by cracking the other distillate fractions of the crude to make lower MW products.

 

Thanks for all the answers and advice to my gas question,

 

Ya want it to run better?

Find or distill your own Moonshine. Pour that in your tank. It will run a lot better! Moon isn't the same crap they put in ethanol gas. I would bet that stuff is probably wood alcohol.

 

Moonshine is hydrated ethanol. Aside from the trace impurities that give it and other distilled spirits "flavor" it is nothing but water and ethanol. Note that pure ethanol is hygroscopic, and anhydrous ethanol (200 proof) will absorb 4% water from the air (changing to 192 proof).

Wood alcohol is methanol, a well-known race car fuel on its own. If the pump says E15 or ethanol, there is only methanol in trace amounts in the fuel. If methanol is present in significant amounts, it has to be stated on the pump.

Shine is typically lower proof than pure 192 proof ethanol... I expect you'll get worse results running a shine mix compared to E10 or E15 pump gas. You'll have both more water in the fuel and fewer miles per gallon. And there are the corrosive and rubber-attacking issues of alcohol fuels.

 

Lets also add that pure alcohol is what 110-115 octane and does not burn well at low compression.