Thursday, May 20, 2010


No, not that kind. The CAR kind.

My mother in law mentioned to me that her car gets better mileage on the ethanol-free variety than on the regular unleaded, so I decided to run a little experiment. Oh, yes, I am FULL of experiments these days. It must be the new house thing, what with needing to realign our lifestyle to accommodate all of the changes.


Here's what I did. I filled up my tank with ethanol-free gasoline and Wayne's Automotive in Monona. I set my trip meter to zero and drove until my tank was low enough to require more gas. I noted both the mileage on my trip meter and the amount of new gas I put in. The new gas was the standard ethanol-filled gas at mobile. I reset my trip meter and then drove my car until the gas gauge was low and refilled with ethanol-free gas at Sinclair.

Want to know what I discovered?

My mother in law is right.

Really really right.

Using the following handy dandy equation, I calculated how far each gallon of gas gets me.

  • # miles driven / # gallons required to refill tank = miles per gallon

Realize, though, that I didn't quite empty my tank after filling it with ethanol-free gas, so the ethanol-filled tank was actually lower in its ethanol ratio than is true to what came out of the pump.

My results:

  • Wayne's gas, ethanol-free: 317miles/9.8gallons = 32.34 miles per gallon
  • Mobile's gas, ethanol-filled: 241 miles/ 13.6 gallons = 17.7 miles per gallon

Can you believe that? I can't. Well, I wouldn't be able to if I hadn't actually written down my mileage and kept very close track of it. From now on, I'm definitely buying the ethanol free gas because even the 10% markup I have to pay for it is swallowed up in the amount of benefit my wallet sees to the mileage for that same tank of gas.

ETA: You may pause here to ask, well, what was my driving style over the 4 weeks of the experiment? To answer:

I drive 60 miles round trip to work 5 days every 2 weeks. This is 80% highway driving.

I drive to town, 50 miles round trip, probably once in that same period, and it's 90% highway.

I drive around town, maybe 2-5 miles each time, about 3-5 times over that period.

So, largely highway, and largely consistent over the period of the experiment.

1 comment:

Jenny Schroeder said...

However, when you were in Montana, were you doing all highway driving? That could also be part of the better gas mileage. I will try that experiment myself - definitely worth it!!