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Posted by D. Sherman on Friday, April 04, 2008 at 11:14:38 :
In Reply to: Re: DUEL FUELS posted by Tim Holloway on Friday, April 04, 2008 at 07:10:42 :
I also remember hearing from the old-timers that since kero was a lot cheaper than gas in the old days, they'd figure out how much kero they could mix with the gas and still have the Model A run. Apparently, they could have 50% or so kero and it would still start and run okay, if rather smoky. This is not too surprising since the quality of the "straight-run" gasoline in those days wasn't very good by our standards, so the engines had to be designed to accommodate it. One neat feature of the Model A that helped with that is the "real-time" spark advance lever on the steering column. You could advance the spark until it just started to knock and then back off. Also, you could advance it as a sort of "cruise control" on straight level roads where you didn't need full throttle, and then back off when you got to a hill.
The oldest "gasoline" engines, the "one-lungers" were often designed to run on kerosene. Every farmer was buying kerosene or coal oil anyway for lamps (and maybe also for killing lice, oiling clocks, and keeping saw blades from sticking) and every country store sold it, whereas gasoline was hard to come by early on. I've always wondered if the brand name, "Oil-Pull", referred to the engines running on kerosene.
In any case, engines have evolved along with fuel improvements, to the point where we now have two kinds of engines optimized for two very narrowly-specified grades of fuel. It didn't used to be that way. Engines were designed to use what fuel was available, which used to be much more variable than today. Modern fuels are "backwards-compatible" with old engines, but old fuels, like a 50/50 gas/kero mix, or low-octane "natural" gasoline wouldn't even work in a modern engine.
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