Thought on using 100 Octane, Low Lead Av-Gas in 4 Cys D-B Engine

[Guest Power Wagon Guy]

 Dodgin' Brothers & Sisters,

 

Its starting to get colder here, but a few good days of touring may be left before years end. If it warms up enough to take my D-B for a ride this winter, I'd like to have it ready to go.

 

With the crappy Ethanol laced fuels, I'm thinking of going with 100 Octane Low Lead Aviation Gasoline from my local Airport. The cost ($5.00 Gal) isn't really a factor, as long as the fuel doesn't do permanent damage.

 

Looking for opinions on possible adverse effects on: Spark Plugs, Aluminum Pistorns, Cylinder Head, Exhaust & Intake Valves, and any other internal parts or engine system ?
 

Any "thoughts' out there if this a good idea or not?

 

Thanks for Any & ALL comments

 

Power Wagon Guy

[ArticiferTom]

Seems like octane level is a little high . I was concerned when I started using 90 oct which is non-ethanol regular . Look around in last  year two different companies with 3 stations started selling non-ethanol here in Pa  with in 10 miles of me . Valero is one but not all there stations offer it . The other is an independent diesel station by interstate . The Valero's are directly own by fuel supply company ,as is third independent ,who sells out of his fuel yard .

 Lead in cars older then 60's I believe didn't require leaded . Other may know better on that .

[C Carl]

P.W.G. : almost certainly EXPENSIVE BAD IDEA ! First off , what is the compression ratio of your engine ? Rule of thumb is 10x compression ratio is aprox octane requirement. For example , gasoline in the early - mid '20s was 40 something. So , therefore my mid '20s Cadillacs have around 4.5:1 compression. The higher the octane , the slower the burn (flamefront propagation rate). The higher the compression pressure , the higher the flamefront propagation rate. Now add the slow rate of high octane gas , to the slow rate of low compression pressure , and you end up not extracting all the power (BTUs) from the combustion before the exhaust valves open. Ultimately , this is hard on exhaust valves. I use the lowest octane , "moonshine free" gasoline I can find. You should do the same on a low compression engine. Now as a note of gasoline info trivia : There is (or was some years ago) octane up to 127 at some locations in the Los Angeles area. What else for the lucky guys/gals to run in their 13:1 competition Ferraris and the like ? I sure wish I could get some 50 octane somewhere. Again , what is the compression ratio of your engine ? - Carl

[Spinneyhill]

I have heard stories of exhaust manifolds glowing a bit red after a long run using high octane fuel in a side-valve engine (after dark of course). So imagine what that is doing to the exhaust valve. The demands on the cooling around the valve seat would be extreme and if your cooling system is not in tip-top condition, you might be doing repairs sooner than you otherwise would.

[30dodge35]

I would not use 100 octane foe extended use. Aircraft reciprocating engines use Sodium filled exhaust valves in order to use high octane aviation gas, do to higher temperatures. We are lucky here in Louisiana, a lot of station have low octane regular gas without ethnol to use on recreation outboard motors,

[StillOutThere]

There are many collections and many restoration shops using 100 LL because ethanol fuels start deteriorating in 2-3 weeks whereas 100 LL will not deteriroate for two years.   I have run some of it in later model collector cars but not enough experience long term.  Can tell you it gave truly instant starts and very smooth running in every car where I used it    The 100 octane rating.is at altitude in a plane.   I will use it again and one place will be my '17 Dodge.

[alsancle]

I have a friend who runs nothing but AV gas in his prewar cars for YEARS.  Never had any sort of issue.  We are not talking hundreds or thousands of miles but occasionally around town.  It never goes bad.

 

I ask anybody that freaks out over this (This thread pops up once a year)  do you have any hard evidence of the high octane gas dong damage?

[C Carl]

Fair enough. As first freak to come foreword , I concur thoroughly with asking someone the source of their information. In my case , it goes back to my flight engineers training about 50 years ago. Trained on recip's , primarily R2800s and R3350s , we were warned of potential damage to exhaust valves by using higher than spec octane. If the only fuel available to an aero engine was of higher than spec octane at the airport of departure , we were advised to take on sufficient fuel for the flight , but no more. I also have considerable experience using gasoline with a greater selection of octane in cars operating from sea level to almost 17,000 feet in South America. If you ran the excellent 96 or 98 octane low altitude gasoline trying to pull a grade at 16,000 or 17,000 , you might not make it. High altitude gasoline was , if my memory serves (this was a long time ago) , around 74 octane. I would carefully fuel my cars and jerry cans to make very sure my octane was as low as possible when adventuring at high altitude. I use low octane gasoline if I am driving above , say , 6000' and on up to 10,000' such as White Pass in California , or even higher when I cross the Continental Divide on Trail Ridge Road in Colorado. Never driven up Pikes Peak. Seems to me something like 85 octane is available locally. Use it if you drive there. Now if you are driving an old car sparingly and infrequently , I don't think you will do any damage. BUT : You quite simply will not develop as much power using 100 octane as you would using 87 octane. Around my state of Washington , I know places where 87 , 90 , and 92 octane "moonshine" free gasoline is available. And is much cheaper than $5 a gallon av gas. In closing , a word about 1917. I believe gasoline back then was primarily hexane and heptane , having an octane rating of 40. There is enormous difference between the fast flamefront propagation rate of 40 octane vs. the much slower 100 octane av gas. Even with 87 octane pure gasoline , you will not have extracted all the B.T.U.s from your fuel by the time your exhaust valves open in your 4:1 or 4.5:1 compression centenarian. Give it a break. Better yet , figure a way to safely and economically blend something into 87 octane to bring it down to 50. I know , fat chance. Thank you very much for asking. So many of us have such varied experience , and how phenomenally lucky we are to have this almost miraculous technology. The collective knowledge we create here is a real treasure. Particularly for us old folk who can't get out and do much anymore , and have lost so many of our best , oldest friends. Oh yeah , in case you haven't figured it out yet , we are extremely lucky to have arrived at our predicament. There are some brave young folk who cheerfully participate here that are prematurely disabled with illness. Count your blessings , oldsters. You made it ! With love and appreciation , - Carl

[ArticiferTom]

What about this ethanol extraction you see being done on you tube ? They add water then rack off . There only complaint is you lose octane ; exactly what we want .  There maybe lose of some detergents and other additives .

    Time for engineers to step up !

[nearchoclatetown]

Tom. I'm no engineer but I ain't paying for something to throw away. On a rainy PA. spring day take a open glass container and let it sit in the garage for a few hours. The corn juice will extract water out of the air and settle to the bottom and be a different color. I do have to say I have not had any trouble like some report with ethanol. I buy from a very busy station, they get filled up a few times a week. It just bothers me our Gov't tries to fool the fools thinking this crap is better. 

Edited December 5, 2015 by nearchoclatetown (see edit history)

[ArticiferTom]

It's not just the ethanol ,but also getting the octane down ie. 87 will drop to about 83 they say . Waste would be the 10 o/o a lot cheaper than av gas or even non- ethanol regular which is about a dollar more per gallon but 90 octane regular .

[Phil 32DL6]

Here's another take:

 

That's what I did (including updating the carb), and so far I've had zero problems after about 8,000 miles on my '32 DL.

[C Carl]

Wow ! Tom , thanks for that ! While I don't think it would be worth the hassle to just get a 4 point drop , it gets me to thinking. What we old car guys need is 40 octane for 'teens , 45 - 55 for early - late '20s , 55 - 60 or so for '30s - early '40s , and maybe 70 something for early post-war. Maybe there might be a market for , say a 50 octane gasoline which will be absolutely perfect for some of us , and a vast enormous improvement for guys with even older cars. The newer cars could easily blend up with a 50/50 mix with 87 - 92 at the pump. Now from the insight I have just got from your enlightening revelations , I see that the base stock gasoline before being polluted with moonshine is 83 octane. I wonder if there is a very low octane gasoline component to E85 ? Something similar to "white gas" , Coleman fuel , naphtha ? Could this pre-adulterated base stock be sold to a friendly distributor ? As I say , very high octane octane gasoline is sold at a large number of locations in the L.A. area. Might there be a greater demand for 50 octane than 127 ? The amount of folk with infinite wealth , and huge collections of brass cars , and what we old guys remember as products of the Classic period of automobile production would love it (are you reading this , brother-in-old-cars Jay Leno ?). Where we 4:1 - 6:1 compression ratio guys would really feel the difference would be in pulling grades. It would pollute much less , get better gas mileage , and run better in all conditions except extreme low rpm. It is much easier to raise octane economically and safely than it is to drop octane. But you have got me to wondering whether at some point in the refinery there is some product significantly superior to 87 octane for us. One of us knows someone who knows someone who knows. Does this make any sense at all ? You have just got me thinking , and I am usually slow to think through things. Yeah , what do youse think ? - Carl

[ArticiferTom]

Thanks Carl ,I guess . That octane reduction was approximate and from only some one source on the internet . Shall Say WEWE !  Repeated by me ,who hasn't a clue . But your right if they made a 50 it could easily be blended up .

  But another thing I read, is that the ethanol is added at the terminal or end of shipped pipe line . This is why distributors that have stations are the ones who have non-ethanol available at there retail stations . They would know what the actual octane of there gas is before adding the ethanol . But would they want the hassle of selling 20-30 gallons there . I mean how would the state get their 20o/o of taxes .

[JACK M]

Just a warning on LL gas. It will kill a catalytic converter.

Race gas and Av gas should not be used in any car or truck that has one.

[cahartley]

The ONLY difficulty I experienced with the "new" gas is with ONE car, my '19 Model T Touring, in which the "new" gas dissolved all the crud in the tank left by OLD gas.

There was some sandy sediment I needed to flush out and never experienced any further problems.

Outside of the occasional addition of some MMO at every other fill I've done nothing.

On the cars I can I shut off the gas, run them until the carbs are empty, disconnect the batteries and walk away for the off season.

[JACK M]

_{Seafoam makes for good storage of gasoline.}