Note on gas prices and choosing grades.

First - if you aren’t already using Gas Buddy to find cheapest gas, time to start.

Second, if you didn’t know there’s a new grade of gasoline called 88 octane, that is actually 15% ethanol. I don’t recommend it, these RX’s weren’t designed for that level of alcohol.

Ok so ethanol has 70% of the energy of gasoline. So if you can drive 1 mile on 100% gas, you’ll go 0.7 miles on pure ethanol.

Almost all gasoline has 10% ethanol, so 1 gallon of gas w/ 10% ethanol has 97% of the energy of ethanol-free gas. Gas w/ 15% ethanol has only 95.5% of the energy of ethanol-free gas.

You can use those percentages to choose grades.

Take the price of ethanol-free gas, and the price of 10% ethanol should be 97% or less to prefer the 10% blend. Again, don’t recommend 88 octane, but it’s price would have to be 95.5% cheaper than pure gas to be worthwhile.

Example:

$5.50/gallon for ethanol-free

97% of 5.50 is $5.34/gallon

95.5% of $5.50 is $5.25

So if 10% ethanol gas is more than $5.34, take the ethanol-free gas. If you’re willing to take the risk, 88 octane should be $5.25 or less.

Now you know…

 

Interesting numbers. I think I'll stick with Premium (no Ethanol), same for my lawn mowers