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Old 11-23-2019, 08:34 PM   #1
njmazzarella
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Default Using 85 octane fuel

Can Model A stock engine safely use 85 Octane gas?
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Old 11-23-2019, 08:40 PM   #2
barkleydave
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Default Re: Using 85 octane fuel

yes especially at higher altitudes

HC head 87 would allow more spark advance
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Old 11-23-2019, 08:58 PM   #3
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Default Re: Using 85 octane fuel

Something of interest, in the mid 1920's octane of fuels ranged from 40 to 60 Octane and big improvements did not show up till later and then much more during WWII.
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Old 11-23-2019, 09:38 PM   #4
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Default Re: Using 85 octane fuel

In my youth one of my buddies was running kerosene as the fuel for his 1928 Tudor. Performance was mediocre but it ran. Octane when the car was new was far lower than any gasoline sold today.
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Old 11-23-2019, 10:12 PM   #5
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Default Re: Using 85 octane fuel

Quote:
In my youth one of my buddies was running kerosene as the fuel for his 1928 Tudor. Performance was mediocre but it ran. Octane when the car was new was far lower than any gasoline sold today.
I don't know if Jack White (John D. White) of East Sandwich was among your buddies but he was my uncle and running a Model A on kerosene during WWII oil rationing. The memory was high on his memory list including having a "switch over" valve to start the car on gasoline, and do the swap on the fly.

Uncle Jack was a bit of an "institution" in East Sandwich - small town boy, long time member of the East Sandwich Volunteer Fire Department, gifted finish carpenter, and beach runner in his later 1930s vintage panel truck popularly known as "The Red Onion."

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Old 11-23-2019, 10:58 PM   #6
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Default Re: Using 85 octane fuel

Quote:
Originally Posted by DHZIEMAN View Post
Something of interest, in the mid 1920's octane of fuels ranged from 40 to 60 Octane and big improvements did not show up till later and then much more during WWII.

One more thing, octane is the measure of how much compression a fuel can withstand before igniting. Or, in laymanís terms, the higher the octane rating, the less likely the fuel is going to pre-ignite (read: explode unexpectedly) at higher pressures and damage your engine. Thatís why performance cars with higher compression engines require higher octane (premium) fuel. The Model A (even with a high compression head) is no where near the engine compression that higher octane gas was designed to protect.


Which goes to prove, use the lowest grade (cheapest price) and be happy.
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Old 11-24-2019, 01:11 AM   #7
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Default Re: Using 85 octane fuel

Wanted to add, we're using alcohol free ( ethanol free) in our A's, the octane rating on it is 91. The old cars love it.

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Old 12-03-2019, 08:57 AM   #8
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Default Re: Using 85 octane fuel

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Originally Posted by Mike V. Florida View Post
One more thing, octane is the measure of how much compression a fuel can withstand before igniting. Or, in laymanís terms, the higher the octane rating, the less likely the fuel is going to pre-ignite (read: explode unexpectedly) at higher pressures and damage your engine. Thatís why performance cars with higher compression engines require higher octane (premium) fuel. The Model A (even with a high compression head) is no where near the engine compression that higher octane gas was designed to protect.


Which goes to prove, use the lowest grade (cheapest price) and be happy.
In town there is a self service e85 fuel station along with other grades, but I seldom see vehicles there. Don't know why. I know my old Massey zenith carb dislikes ethanol fuel and I venture it really would not care for E85. The old vintage float valve is rubber tipped and every once in a while when I only had ethenol around, that float valve on occasion got kind of sticky.
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Old 12-04-2019, 09:52 AM   #9
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Default Re: Using 85 octane fuel

E85 high ethanol fuel reduces the mileage since it has to burn more to get the same power output. Flex fuel computer controlled vehicles can run the ethanol or straight gasoline. On the carbureted engines, the jets would have to be changed to run high ethanol fuel effectively.

E85 isn't the same as 85 octane so folks have to be specific about which they are referring to. 85 octane gas is usually only found in mountainous states with higher altitudes to deal with. It's not available where I live.
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Old 12-04-2019, 10:27 AM   #10
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Default Re: Using 85 octane fuel

FWIW, most e85 gas is about 108 octane.
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Old 12-04-2019, 10:32 AM   #11
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Default Re: Using 85 octane fuel

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Originally Posted by ryanheacox View Post
FWIW, most e85 gas is about 108 octane.
Right. Just full of more corn alcohol compared to regular 87 which has 10% or less. E85 can have as much as 51-83% alcohol.

I've never run across 85 regular gasoline. Interesting.
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Old 12-04-2019, 11:00 AM   #12
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Default Re: Using 85 octane fuel

I've got a gasoline globe from the mid-thirties from a gasoline distributor from Missouri. ' Mann's 68'.

68 Octane was considered hot stuff back in this days. They wouldn't have known what to do with 85 Octane
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Old 12-04-2019, 03:46 PM   #13
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Default Re: Using 85 octane fuel

Government mandates follow contents of motor fuel pretty closely. E85 should be very close to 85% fuel grade ethanol with the rest being normal unleaded gasoline. The ASTM allowance was for winter starting since manifold preheat would be required with a full 85% fuel grade ethanol. Winter grade has to be closer to 51% or the tax payers would have a cow. In the warmer climates it is pretty close to 85% so the ASTM used 83% as part of the equation.

Octane is more of a gasoline thing since gasoline based motor fuels have to have an anti knock index. The lower the compression, the lower the antiknock index can be. Ethanol cools the fuel charge naturally so an anti-knock index would confuse the hell out of people. Folks have equated the anti knock index with more power for years so they would think that E85 was rocket fuel but it takes more of it to make the same power as gasoline.
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Old 12-04-2019, 03:50 PM   #14
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Default Re: Using 85 octane fuel

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Originally Posted by rotorwrench View Post
Government mandates follow contents of motor fuel pretty closely. E85 should be very close to 85% fuel grade ethanol with the rest being normal unleaded gasoline. The ASTM allowance was for winter starting since manifold preheat would be required with a full 85% fuel grade ethanol. Winter grade has to be closer to 51% or the tax payers would have a cow. In the warmer climates it is pretty close to 85% so the ASTM used 83% as part of the equation.

Octane is more of a gasoline thing since gasoline based motor fuels have to have an anti knock index. The lower the compression, the lower the antiknock index can be. Ethanol cools the fuel charge naturally so an anti-knock index would confuse the hell out of people. Folks have equated the anti knock index with more power for years so they would think that E85 was rocket fuel but it takes more of it to make the same power as gasoline.
It's the alcohol levels that the turbo charged LS Chevy guys like about E85.
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Old 12-05-2019, 09:38 AM   #15
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Default Re: Using 85 octane fuel

Growing up a neighborhood high school buddy drove a 1931 Model A coupe that his grandfather had left him.This was when we were in Junior year 1963 and he always bragged how it would only run on high test gas. The car was probably all original and poorly maintained,it was solid but surface rust entire body and fenders. The grandpa also left the family his gas station store which has been moved to our fairgrounds now with the original visible gas pumps.Extra cost of high test Sohio was not an issue but even I at age 17 knew it was nothing to brag about evidently valves,compression or spark required higher octane to run somewhat normal. My dad always supported me in search for my own Model A and helped me buy a 1930 roadster in 1964 but a couple years earlier,probably more than that about 1960 a cpuple guys were in the gas station and offered my buddy's dad $500 for the coupe. My dad told me he did not believe it and no way they would have turned down almost its new car price in '31. We paid $800 for the roadster 4 years later.
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Old 12-05-2019, 09:46 AM   #16
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Default Re: Using 85 octane fuel

Racers run ethanol (sometimes with other additives) but they have to burn a lot of it to make the power they want. It runs cooler so it will definitely make good power but it just takes a lot more of it. There is about a 20 to 25% difference on the average.

Last edited by rotorwrench; 12-05-2019 at 09:54 AM.
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Old 12-05-2019, 10:19 AM   #17
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Default Re: Using 85 octane fuel

Please note as Rotowrench says in post #9 ...



Post #1 is asking about 85 OCTANE gasoline NOT E85 Ethanol CRAP "gas".


When I first read it , I also thought that the question was about Ethanol.

Last edited by Benson; 12-06-2019 at 02:35 PM.
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Old 12-05-2019, 12:31 PM   #18
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Default Re: Using 85 octane fuel

njmazzarella,

About post #1:

Yes 85 Octane is perfectly safe ... we have been using it since 1962.

What it boils down to is that the higher the altitude the lower the octane that is required.

Applies to new cars also ...

50 years ago when I worked in the "Flat Lands" on East coast (Ft Monmouth '67 and '69), West coast and Texas the octane numbers were:

At 5000 feet:
85
87
91

at sea level:
87
89
93 and up

Sunoco 190 was 86 in 1960s
Sunoco 260 was 104

Since you are asking you must live at 4000 or more.

Last edited by Benson; 12-07-2019 at 08:43 AM. Reason: blue
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Old 12-05-2019, 01:57 PM   #19
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Default Re: Using 85 octane fuel

Aircraft use high octane fuel for a different reason than altitude so higher octane fuel will still work at high altitudes but it is less necessary for lighter duty automobile engines.

At high altitude, there is less air so less fuel is needed to stay in the operable mixture range. It's generally cooler at high altitude as well. Avgas is not all that volatile so that it won't vapor lock but it has a lot more expensive blend of fuel plus the use of tetra ethyl lead.

A lot of it boils down to cost per gallon too. When I lived & worked in the Rocky Mountain region, the fuel volatility would go way up for winter use. If a sudden warming trend happened, the fuel system vapor lock started to show up bad. Mountain states usually are farther from the sources of fuel and that really drives the cost up. Use of the lower price blends is more common due to that as well.
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Old 12-05-2019, 02:23 PM   #20
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Default Re: Using 85 octane fuel

Hallo und guten Abend
Quote:
Originally Posted by rotorwrench View Post
Racers run ethanol (sometimes with other additives) ...
There are also fuel blends that use methanol instead of ethanol. Methanol enables performance increases >50 %. It cools five (!) times more than gasoline. The fuel consumption doubles.
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