MTFCA Forum

Over the past several years I have run Nellie, my 23 runabout, with several different carburetors just to see the difference. These included the stock Ford stamped NH type that came with my car, a straight through NH, a Stromberg OF and I’m currently running a U&J. I also try different oils and gasolines. Living in the Northeast I switch to a lower viscosity oil in the winter than the summer since I do drive in the cold weather. I also typically use ethanol free gas just because I want less water in the tank. I use no additives in the oil or gas. The ethanol free gas is higher octane (don’t remember the rating). I have the feeling that my car runs better and gets better milage with the lower octane (aka regular). Is this expected .. typical ?

I'm not a chemist nor a petroleum expert, but I would suspect you are correct that the car gets better mileage on the lower octane.
First, when I was in my teens I tried the "super high octane Sunoco" in my first car, thinking it would perform better and get better mileage. For all the extra expense, the dang thing got far WORSE mileage than ever! Never did that, ever again!

Second, kind of think like this comparison: You build a nice fire in your fireplace. Feels pretty good. So you "stoke it" even more, really blazing away. Sure, you get a bit more heat radiating out, but FAR MORE goes up the chimney. Kind of the same with high octane fuel in a car that was not designed for it in the first place. The extra heat (power) is going out your exhaust pipe. Just my unscientific logic!!

If I can remember correctly, the high octane gas was formulated for high compression motors. It was made to burn slower to prevent pre ignition ( spark knock ) In a low compression motor, you need fast ignition to create the most power and best milage.

Thought I do a bit of searching the internet on the development of Gasoline related to the Model T. I found some interesting information and tried to get more than one reference to support what I found. Whatever owners use in their cars likely supports their engine configuration & driving habits. What was most interesting were references to Ethanol
The link follows the related text
"Beginning in the late 1910s through the 1930s, researchers identified engine and fuel relationships between knock, compression ratio, performance, and efficiency "
https://www.frontiersin.org/articles/10 ... 00016/full

"Ethanol is nothing new; Henry Ford built the first Model Ts in 1908 to run on ethanol/alcohol and Standard Oil began blending it as early as 1920 to boost octane and reduce engine knock. Prohibition put a stop to the Ethanol production, for a while. In 1940, the US Army built the first Ethanol plant in Omaha, Nebraska, to supply blended fuel for the military." >>>
https://www.rvrepairclub.com/article/rv ... f-ethanol/#

"By the mid-1920s, gasoline was 40 to 60 Octane." >>> https://www.thoughtco.com/history-of-gasoline-1991845
"Gradually, volatility gained favor over the Baumé test, though both would continue to be used in combination to specify a gasoline. As late as June 1917, Standard Oil (the largest refiner of crude oil in the United States at the time) stated that the most important property of a gasoline was its volatility. It is estimated that the rating equivalent of these straight-run gasolines varied from 40 to 60 octane and that the "High-Test", sometimes referred to as "fighting grade", probably averaged 50 to 65 octane."
Further down in this article
Leaded gasoline controversy, 1924–1925 With the increased use of thermally cracked gasolines came an increased concern regarding its effects on abnormal combustion, and this led to research for antiknock additives. In the late 1910s, researchers such as A.H. Gibson, Harry Ricardo, Thomas Midgley Jr. and Thomas Boyd began to investigate abnormal combustion. Beginning in 1916, Charles F. Kettering began investigating additives based on two paths, the "high percentage" solution (where large quantities of ethanol were added) and the "low percentage" solution (where only 2–4 grams per gallon were needed). The "low percentage" solution ultimately led to the discovery of tetraethyllead (TEL) in December 1921, a product of the research of Midgley and Boyd. This innovation started a cycle of improvements in fuel efficiency that coincided with the large-scale development of oil refining to provide more products in the boiling range of gasoline. Ethanol could not be patented but TEL could, so Kettering secured a patent for TEL and began promoting it instead of other options. ">>> https://en.wikipedia.org/wiki/Gasoline

"In the early 20th century, automotive manufacturers were searching for a chemical that would reduce engine knock. In 1921, automotive engineers working for General Motors discovered that tetraethyl lead (better known as lead) provided octane to gasoline, preventing engine knock. While aromatic hydrocarbons (such as benzene) and alcohols (such as ethanol) were also known octane providers at the time, lead was the preferred choice due to its lower production cost. Leaded gasoline was the predominant fuel type in the United States until the U.S. Environmental Protection Agency (EPA) began phasing it out in the mid-1970s because of proven serious health impacts." >>> https://www.eesi.org/papers/view/fact-s ... -of-octane