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bob duffer
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I use ethanol free 91octane in all my cars and scooters both antique and daily drivers from 1933 thru 2003.  They only sell 91 octane locally that is ethanol free.

 

I was getting vapor lock in the 1933 Chevrolet when I was using gas with ethanol and it stopped happening when I found the ethanol free gas.

 

I add a few oz. of synthetic 2T two stroke scooter oil per tank to my cars with no catalytic converts.  Same oil as I use in my two stroke 1964 Vespa scooter.

 

It cost around 10% more than the local premium gas with ethanol and I get 10% better gas mileage, so it is a break even deal in my modern cars (2002 BMW Z3 and 2003 Mini Cooper S).

 

I have found the government estimates on how much lower mileage you get with ethanol gas is way under estimated.  Most of what I have read from government propaganda says 3% where 10% is more realistic for me.

Edited by Vila (see edit history)
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If you can get gas without ethanol in it, whatever the octane, use that. Ethanol is really tough on old fuel systems, especially if you have older rubber components that aren't ethanol compatible.

 

But in our old cars, premium fuel doesn't really do anything and with these ancient ignition systems, the cars may actually run worse on higher octane fuels because of their higher resistance to ignition. Even the cheapest, crappiest gas to day is much higher in octane than what was being used when your car was new (I think my '41 Buick owner's manual recommends 71 octane for best performance). Remember that the high octane stuff doesn't have anything else in it that makes it better, just a higher resistance to detonation. If your car doesn't knock on the cheap stuff, that's all you need. Putting "the good stuff" in won't do anything except drain your wallet a little faster. If you don't need the octane, you don't need premium, everything else is the same (except for the ethanol, if you can avoid it).

 

Hope this helps!

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Good morning Bob and all. This discussion comes up from time to time in various forms. Octane rating refers to flamefront propagation rate at standard conditions. The higher the octane , the slower the rate. Significant factors which may deviate from the standard are principally engine compression ratio , and ambient air density (principally altitude dependent). These are determinant factors for compression pressure , for which octane requirement decisions will be made. The higher the compression pressure , the greater need for higher octane. A general rule of thumb is 10x compression ratio will be the optimum octane. In the 1920s gasoline octane was in the 40s , thus engine compression ratios needed to be in the 4.5:1 range. The '30s saw 50+ octane , and commensurate compression  ratios. 1940s gasoline octane higher yet. I expect postwar gasoline might well have benefitted from military and aviation necessities , and particularly OHV engines could take advantage of 70+ octane. By the late '60s , some engines had over 10:1 compression , and gasoline was available at the pump for them. Racing gasoline for the sometimes 13:1 engines will be around 130 octane. I had heard that gasoline up to 128 octane was (is ?) available at some gas stations in the L.A. area , though I haven't seen it , and sadly do not have any cars which require it. Maybe in some parallel universe I have my racing Ferrari Testa Rossa or GTO , or a Maserati 450S. Not gonna happen around here. I did , however , occasionally treat my '70 Cad to the available 100 or 110 octane when I was in L.A. with it. It ran much better. I was younger back then , and enjoyed using the power of those 10:1 472 cubes. Got the occasional speeding ticket. At that time I could afford not only them , but the seemingly exorbitant $5 a gallon when pump premium was under a buck. 

 

We all know what happens when you run too low octane. Pre-ignition. Detonation. You will not notice a light dose of this. But you will not develope the power your engine was designed to give. Loads go up as your engine tries to compress an explosion. Over time this will result in premature engine failure. By the time you actually HEAR pinging , this is a condition known as severe detonation. Uh , you know what this means. So so what happens if you run too HIGH octane in a low compression engine , or when driving at high altitude ? First , the explosion will be too slow , and not be complete as the exhaust valves begin to open. This means that you will not extract all the B.T.U.s as power , and will be wasting fuel as hot dirty exhaust instead. Exhaust valve temp goes up , and in extreme cases over time , you burn the ex. valves. Yeah , you are wasting money with less power and potential engine damage to show for it. All this being said , in the real world where we use a light throttle on our precious antique machinery , how much difference does it really make ? In a car designed to run on 45 , or 70 octane gasoline , using already way too high octane , 85 - 93 , does it make a difference ? 87 octane ? 91 octane ? Yeah , you could put in an E.G.T. thermometer , and you woud see a bit of an increase. Pull a long steep grade at high altitude on 93 octane , you will be slower and have to downshift more early and often than on the available inter mountain (U.S.A.) 85 octane high altitude gasoline. Way down South America , high altitude Andean gasoline is is in the '70s octane , and you better have naught but it in your tank if at 13,000 or 17,000 feet going up bound. You know , I think this covers the subject for the moment. You airplane pilots , and old flight engineers will have a deeper knowledge of this than the average earthbound non-competion driver. 'Gear up , climbing out , you want all conditions optimal. All those engine related dials up in the cockpit of old heavy pre-computerized aircraft , allow the pilot or flight engineer to optimize engine performance , and to monitor engine condition. Octane requirement is one of the critical factors. If you are not a pilot , and have never done so , see if you can get an explanation of every indicator in an old multi-engine heavy. See if you can sit at the flight engineers panel which was in charge of 4 R-2800s. Or maybe even R-3350s. As automotive guys , we can get a good understanding , which will relate to our vehicular passions in some ways. 

 

Happy , safe , sane Independence Day ! If you are as old and delicate as I am , don't go overboard at the barbecue. Hear ?  - Carl

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I just pour the regular Mobil 87 octane with a touch of the corn. That all goes into a '48 Packard 288, a '60 Buick 401, a '64 Riviera 425, an '87 Buick 3.8. a '94 Chevy LT1, a '98 Tahoe 350, an '05 5.3 Chevy, a '39 Alley Cat, and a Kaw powered Deere. I think the important part is that I use a brand name gas, the tanker always says Mobil, it's a busy station, and I don't price shop. Seems to be a good plan so far. I do always make sure I take the long way home; gets everything all warmed up and keeps me adding fresh.

 

On the aviation side, when I was a kid my Navy ship still had all the JP5 apparatus for supporting the first carrier based squadron of FH-1 Phantom jets. That was left from qualifying the pilots the year I was born, 1948.

Bernie

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Bernie, dang, you're an old guy:PYou and I are the same age, but, I'm better looking:lol:   The youngest daughter tells her mother that I remember when dirt was new.  Anyway, back to the show here - I run 100% pure gasoline in all of my old Buicks and they seem to like that stuff pretty well.  They run great on it.

 

Terry Wiegand

Out Doo Dah Way

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My problem, was not the issue of gas quality, but the issue of evaporation of the vodka that's put in.

I did a loooooooooooong thread about this and a 1933 Marvel carburetor design, WHICH may be a lot of the problem. ( low speed jets)

I grew up with Ethyl or Regular. Who used Ethyl, the rich people I guess, I'd work for 4 gallons of gas to keep my 1953 Pontiac Chiefton Deluxe running.

If not, couldn't pick up the girlfriend which was critical.  

I just fill em and drive em.  

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On 7/3/2016 at 11:49 AM, Matt Harwood said:

If you can get gas without ethanol in it, whatever the octane, use that. Ethanol is really tough on old fuel systems, especially if you have older rubber components that aren't ethanol compatible.

 

But in our old cars, premium fuel doesn't really do anything and with these ancient ignition systems, the cars may actually run worse on higher octane fuels because of their higher resistance to ignition. Even the cheapest, crappiest gas to day is much higher in octane than what was being used when your car was new (I think my '41 Buick owner's manual recommends 71 octane for best performance). Remember that the high octane stuff doesn't have anything else in it that makes it better, just a higher resistance to detonation. If your car doesn't knock on the cheap stuff, that's all you need. Putting "the good stuff" in won't do anything except drain your wallet a little faster. If you don't need the octane, you don't need premium, everything else is the same (except for the ethanol, if you can avoid it).

 

Hope this helps!

 

Once again,, Matt is right on target

 

I use only Non-ethanol 87 Octane at home, and any Non-ethanol I can find when travelling

I pay $2.29 at home, and paid $3.49/gallon today in Salem, Ohio on the CCCA Mini-CARavan

 

THe lowest octane  available will help reduce vapor lock, and I sometimes add 10% Diesel to my gas in the old cars for this purpose - It will smoke a bit, but really helps, and you may just help to reduce the mosquito population....

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Looking forward to meeting you on Saturday, Marty! Haven't decided if I'm bringing the '29 Cadillac or maybe one of the '41 siblings. I bought the '29 in Salem, maybe I should take it back to see its old friends there...

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