Saturday, June 25, 2011

Cheap Gas

How far is it worth driving for "cheap gas?"

Let's say I have a gas station near me (or on my route or whatever), but that I know another gas station elsewhere is selling gas for ten cents less. Is it worth it for me to go out of the way to buy it cheaper?

When I fill up, I usually get about 12 gallons. So, the trip must be worth $1.20 for me to make it. Since gas is about $3.60 right now, I am saving about 1/3 of a gallon of gas to get to this other station.

My car gets about 27 miles to the gallon, so to be worth the 1/3 of a gallon, it must be less than 9 miles (round trip) for me to go out of the way to get it and come back.

This seems like a decent open-ended question for students to fill in with their own numbers for their cars.


  1. This is an excellent question for getting students talking about practical math. Thank you!

    - Elizabeth (aka @cheesemonkeysf on Twiter)

  2. Love this.

    May I observe that this assumes that your time is worth nothing?

    I would maybe be more convinced by a model that incorporates some reasonable hourly rate for gas-fetching services. Say minimum wage. No idea what that is right now (fortunately). But if we did know that, then we could factor the cost of your time into things. And I'm gonna be surprised if it's ever worth your time.

    I have tried this argument with my father. He will not listen. He evidently believes not only that his own time is worth nothing, but also that the time of everyone else in the car is worth nothing.