Quote:
Originally Posted by 2000mc
but at what price are the fuels of equal value? i've heard E10 has 3-6% less btu's. even going with 3%, i'd be losing money paying more than $3/gal, i'm thinking.
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This is clearly a YMMV thing, as some cars react better to E10 than others. Because while E10 does have slightly less BTUs, it does have other desirable burn properties (higher octane for example) that can in some cars overshadow the BTU loss (and in some cases actually increase FE in some cars). For example, my car doesn't seem to care much if it has E10 or not, and sometimes even gets better FE with E10 than it does with plain gas. Which kind of makes it hard to generalize, as each car behaves differently to E10.
However, if you assume that just the BTU difference is the only factor (and as already mentioned its not), the break even math works out to:
gas_price = E10_price / (1 - E10_BTU_loss_percentage)
Or, assuming a 4% loss for E10, we get:
gas_price = E10_price / (1 - 4%)
or
gas_price = E10_price / (1 - .04)
or
gas_price = E10_price / 0.96
So, again assuming the assumptions of a 4% loss for E10 are correct, you get "break even" if/when your gas_price is equal to (
E10_price divided by 0.96). Likewise, gas would be a better deal (again assuming those assumptions) if/when "
gas_price < (E10_price / 0.96)", and E10 should be the better deal if/when "
gas_price > (E10_price / 0.96)".
Again, that's just the math involved. Feel free to plug in your own numbers (with your own assumptions), and figure out what price differential makes it most "cost effective" for you. Likewise, remember that it's not all about BTUs, and so your assumptions (and therefore the math, above) might not reflect reality in any given car.
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