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Old October 22, 2012, 11:12 AM
Canker Canker is offline
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Join Date: Jan 2010
Posts: 95

My cat hasn't gone to math class lately, so my calculations may not be 100%.

I'm going totally off topic here and risking future anal seepage because I wanted to point out that 87 octane gas in BC has "up to" 10% ethanol (it's 10%!), while 89 and above generally does not. Ethanol has about 2/3 (66%) the BTU gasoline does.

If you're buying 75 liters of 87 octane fuel at $1.29 per liter the cost is $96.75. If you calculate 10% of this as ethanol (7.5 liters) at 2/3 the BTU, this ethanol is roughly equivalent to about 5 liters of 87 octane gasoline without ethanol (.66 * 7.5). So, your 75 liters of fuel is actually more like 72.5 liters without ethanol. (75 - 2.5, or 96.6% of 75 liters of gas without 10% ethanol).

To find out if it's worth buying 89 over 87, simply take the cost of 87 octane per liter and divide it by .966. If it comes out costing more than one liter of 89 octane gas, fill up with 89. Also, if you're going on a longer trip filling up with 89 should mean filling up a little less often. People I know with fancy schmancy mpg counters in their pimp mobiles have confirmed to me they do get better fuel economy using 89 over 87 anyway, and this anecdotal evidence got me to actually figure this out one day.

Originally Posted by Perineum View Post
People going to a gas station is a perfect example. If someone else was paying for gas most people would chose 94 octane to fill their car with, regardless of the brand or model of their car..... because they'd want the "good stuff". 94 is better than 87, right? Truth is, higher octane is the ability of gasoline to resist burning. Higher octane gas will run worse in your daily commuter than 87 would.
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