The Most Scientific Experiment I’ve Done Since High School

A few weeks ago, I blogged about this cool app they offer at a local gas station, Cumberland Farms, where you can pay right from your phone and it gives you a discount of 10 cents per gallon off their posted price. You can read all about it here. But as I mentioned before, I’ve always felt like I got fewer miles per gallon when I fill up with the cheap gas at Cumberland Farms than when I fill up somewhere more expensive. So I have never been 100% convinced that buying gas at Cumbies is the better deal. I therefore set out to do a scientific experiment, wherein I would determine once and for all if the lower price at Cumberland Farms really does mean fewer miles per gallon. This experiment was in fact, so scientific, so official, so professional, that it only felt right to tell you about it in traditional “Scientific Report” format. Keep in mind that I haven’t written one of these bad boys in about 7 years though, so I’m most likely doing it wrong . . .

Maybe these glasses will help me sound like I know what I'm talking about.

Maybe these glasses will help me sound like I know what I’m talking about.

Kelsey’s Gas Station Experiment

Question: Does the gas I buy at Cumberland Farms get gas mileage that’s as good as the gas at Irving? Is it worth saving 20 cents per gallon at Cumberland Farms or is the more expensive gas at Irving getting me further?

Hypothesis: If I fill my tank up at Irving for 20 cents more per gallon, then I will get significantly better miles per gallon than I will if I fill up my tank with the cheaper gas at Cumberland Farms.

Methods and Procedure:

  1. Fill up tank at Cumberland Farms.
  2. Record following info: previous mileage on car before I filled up, price per gallon, total gallons purchased.
  3. Drive around! The fun part. It’s also important to note that I had approximately the same mixture of city vs. highway miles with both kinds of gas. I drove around town, to my job, etc. on both tanks but also completed on trip to and from Portland to Boston with each tank. Cause I’m thorough like that . . . 🙂
  4. Once tank is empty again, repeat steps 1-2 at Irving. Be sure to record final mileage when tank filled at Irving is empty.
  5. Ask Katie to help me do some calculations. Math is the worst.


Miles/ Gallon = (Miles After Filling Tank – Mile Per Filling Tank)/ Total Gallons Purchased

Price/ Mile = Price Per Gallon/ Miles Per Gallon

The difference in miles per gallon would be considered significant if it caused a difference in Price Per Gallon of more than 10 cents.

Results & Analysis:

Cumberland Farms

Miles Per Gallon: 25.6

Price Per Gallon: $3.539

Price Per Mile: $0.13


Miles Per Gallon: 27.3

Price Per Gallon: $3.759

Price Per Mile: $0.13

So pretty much hypothesis was incorrect! FAIL! There’s no significant difference between gas vendors. At both Cumberland Farms and Irving I got the same price per mile. This means the choice is: I can either pay a little less per gallon, but not get quite as much mileage; or I can pay a little more per gallon, but get a little more mileage out of your tank. With the cheaper gas at Cumbies, the total to fill my tank will be a few dollars cheaper. But with the better mileage at Irving,I might be able to drive a few more days before you need to fill your tank again. The good news is, I can’t really go wrong either way.

I guess all of that math and science in high school really did pay off . . .


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