Am I crazy? MPG on “Crap gas”

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downforce137

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the ethanol content with shell or amoco is probably higher than the lower tier, which would quickly and easily explain the better mileage with lower ethanol content..
 

grendel

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Wouldn't octane and ethanol content affect MPG? I'm not sure "cheap" vs "expensive" helps without more info. I see slightly (maybe?) better mpg with 93 vs 91 octane, but, in reality, there are too many variables in driving.
 

spack

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I’ve tried this experiment as well… several tanks, regular vs premium. I can’t detect a difference when I’m trying to get good milage with a soft touch. Ethanol content aside, the energy content of regular vs premium is the same. The flashpoint or anti-detonation of premium is higher due to hexane content, allowing the engine to run higher boost, thus more fuel under load. More advanced ignition timing as well. I would theorize that under higher engine loads you “may” get less milage out of premium because the knock limits imposed by the ECU on regular will self limit the engines power output thus less fuel. Higher boost, more advanced ignition timing, and secondarily more fuel with premium. But I’d think if you are not pushing the truck premium vs regular would be hard to detect. And as stated by someone. Wind load, and hills might push the engine to a point where the operating parameters of regular vs premium are quite different.
 

DaveInMn

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I’ve tried this experiment as well… several tanks, regular vs premium. I can’t detect a difference when I’m trying to get good milage with a soft touch. Ethanol content aside, the energy content of regular vs premium is the same. The flashpoint or anti-detonation of premium is higher due to hexane content, allowing the engine to run higher boost, thus more fuel under load. More advanced ignition timing as well. I would theorize that under higher engine loads you “may” get less milage out of premium because the knock limits imposed by the ECU on regular will self limit the engines power output thus less fuel. Higher boost, more advanced ignition timing, and secondarily more fuel with premium. But I’d think if you are not pushing the truck premium vs regular would be hard to detect. And as stated by someone. Wind load, and hills might push the engine to a point where the operating parameters of regular vs premium are quite different.
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You make some good points.
I found a good article on this topic called: "Premium Gas vs Regular - Is It Worth It?" It even brings corn-gas into the discussion. Enjoy! :favorites13:

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