Quote:
Originally Posted by Fenring
When thinking how could lower octane fuel beget better performance, I'm leaning more toward the explanation that it might have something to do with energy density of fuel which can vary with additives. Although I find it hard to believe such differences would be noticeable.
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The literature on this is pretty conclusive - although energy densities of different fuels do vary slightly (again, notwithstanding things like ethanol vs. non-ethanol fuels), this is not correlated to octane rating. While I can't speak to the experience that an engine runs better/worse on higher/lower octane fuels (with no other changes), there really isn't much of a technical footing here. But you can't discuss this subject without noting that a person's perception of how an engine runs is subjective to begin with and then there are tons of confounding influences (ambient temperature, humidity, variations in engine tune, etc.). And "butt-dynos" are notoriously inaccurate. Doesn't one of the motor oil commercials prey on our perceptions here to say that you can just "feel" how much better an engine runs when you use their brand of motor oil? Technically, it just doesn't hold water.
I know for an absolute fact that every one of my vehicles runs much MUCH better after I wash it. Every one.
- Mark