PRICEisWRONG

Hi folks. I just myself a 79 Coupe, and it still has the original 350Ci engine it. I know these cars were not designed or tuned for Ethanol, so what would be the lowest Octane that should go in it?

MelWff

the engine is low compression and unmodified can run on 87 octane.

zwede

E10 pump gas is fine.

cv67

W/Mel. Id still put premium in it especially with iron heads. Not worth saving $3.00 for a tankful if the thing starts pinging and hurting itself.
Gas is cheap, engines arent

Iceaxe

Load the app "Pure Gas" on your smart phone, it will tell you where ethanol free gas is available in your area. If you are lucky like me there will be several gas stations nearby that sell ethanol free gas at a reasonable price. I pay less than 10 cents a gallon more for ethanol free gas and it eliminates numerous problems in the old carbarated cars and boats.

Capt. Shark

That's an excellent app and mostly accurate. The ethanol free gas here is .40/gal more but I think it is still worth it. My 370Z doesn't seem to care but I'm not putting ethanol gas in my old Vette.

71 Vert LS1

I run 91 octane in all my hot rods. All LS swaps. No corn for me.

C3 4ME

I run 10% ethanol in my 79 and have been for the 13 years I've owned it with no problems. While I still have the original engine, it's not stock, so I run 89 octane.

derekderek

Lucky the gas tanks aren't fiberglass. The ethanol dissolved the resin out of the fuel tanks of my old 34 Hatteras. Deposited it on the valve stems. 2 years of swapping heads til I could replace the fuel tanks.

cv67

It literally glued up every passage in my 850, in fact old gas wouldnt even fire period, just fouled plugs

Bikespace

I run 93, 10% ethanol, in my two L48s. My wife insists on 93 in hers, and Shell 93 at that, based on the advice of others. I tried 87 in my 80, and it ran hot, dieseled at shutdown, and generally didn't like it, so I'm back to 93 there, too, but I usually frequent a nearby Exxon station that services classic cars.

I could save 10% on gas by running 87, maybe. Or I could save a bunch of money on gas by selling the Vettes, but that would miss the point! The nearest ethanol-free gas is nearly an hour away, but I buy it for my lawnmower.

7T1vette

Putting higher octane fuel in a low compression engine is just wasting money. There is no "value added" for spending money on what the engine cannot use.

Pump regular is fine for L-48 engines from '71 and up. If you can't get it to run well, your engine has other "issues".

derekderek

The issues being it has timing recurved for slower burning higher octane fuel.

Capt. Shark

I think the concern is not necessarily the octane rating but the added ethanol in a fuel system that was not designed to have alcohol run through it and/or sit for long periods of time.
Alcohol and rubber don't like each other.

7T1vette

I would agree that having ethanol fuel in the fuel system and then storing it for long periods of time is not a good thing. If you are going to store the car with fuel in it, put 100% gasoline in it first.

DorianC3

Folks that are more knowledgeable can chime in, but I have read and found evidence that there are other issues with ethanol.

It purportedly changes the density of the fuel and throws off your float level setting. It also evaporates out of the fuel first, leaving the carb vulnerable to varnish and gumming up if not driven frequently.

HeadsU.P.

Using my knowledgeable college and automotive expertise wisdom from decades of hands-on wrenching, problem solving and technical inspections of not so elaborate fuel systems, I will make this very mature statement about Ethanol:

I HATE IT - I HATE IT - I HATE IT ! ! ! !

Capt. Shark

But the .gov always knows what's best.

calwldlife

C/R is still the main reason an octane is used.
as stated before,
the alchyhole burns different than pure gas.
speed and air/fuel percentage.
increase fuel percent by about 10-14% (not a/f ratio but jet size)
and retime the distributor spark
advance curve to come in sooner.
alchy needs a little richer a/f ratio to act like gas.

71 Green 454

Me too! I have 2 Wawa stations near me that sell ethanol free gas. I just returned from filling up my lawn equipment gas can.