# Can I calculate the energetics of a gallon of gas?
**URL:** https://boards.straightdope.com/t/can-i-calculate-the-energetics-of-a-gallon-of-gas/391902
**Category:** Factual Questions
**Created:** [February 12, 2007, 7:10pm UTC](https://boards.straightdope.com/t/can-i-calculate-the-energetics-of-a-gallon-of-gas/391902 "2007-02-12T19:10:25Z")
**Posts on this page:** 2
**Page:** 1
### Author:  [@Emilio\_Lizardo](https://boards.straightdope.com/u/Emilio_Lizardo)
#### Post date: [February 12, 2007, 7:10pm UTC](https://boards.straightdope.com/t/can-i-calculate-the-energetics-of-a-gallon-of-gas/391902/1 "2007-02-12T19:10:25Z")
I’ve noticed that some of the gas stations around here are consistently 10 - 15 cents per gallon cheaper than the others. These same stations also have a small notice on the pump saying that the product they dispense “may contain up to 10% ethanol.” Now I know ethanol is less energetic then gasoline. Is there any way to a quantitative analysis of which is the better deal on an energy/price basis – higher energy, higher price vs lower energy and lower price? Despite the “may contain” in the disclaimer, I’m willing to assume that any company the CAN sell up to 10% ethanol WILL be selling 10% ethanol. This will make the calculation easier.
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### Author:  [@zut](https://boards.straightdope.com/u/zut)
#### Post date: [February 13, 2007, 12:58am UTC](https://boards.straightdope.com/t/can-i-calculate-the-energetics-of-a-gallon-of-gas/391902/2 "2007-02-13T00:58:47Z")
Short answer: ethanol contains pretty close to 2/3 the energy of gasoline. There’s some variation depending on what blend of gasoline and so forth, but that’s pretty close. So with a 10% ethanol blend, you’re losing 1/3 of 10% of your energy, or 3.3%. Unless you’re paying well over $3.00, your 10-15 cent savings sounds pretty good.
[Wikipedia](http://en.wikipedia.org/wiki/Gasoline) has the volumetric energy density of some fuels compared to gasoline, including ethanol and 90/10 blend.