What is the MPG of a Human?

Whilst driving home from work last week an interesting thought popped into my head. I noticed a bicyclist going up a steep incline and thought "that can't be very efficient." Then one thought led to another and I ended up with the question "what would the mpg of a human be?"

     What is the MPG of a human being? This is an interesting thought experiment that has little to no actual scientific value. For this to be remotely plausible humans would have to develop the ability to digest gasoline, which doesn't seem likely to happen anytime soon. But if humans could somehow convert gasoline into energy what would the optimal miles per gallon be for the average adult male?

     Well lets begin by seeing how many calories are in a gallon of gasoline. This works because calories are a measure of energy. We use gasoline for energy to power our cars so common intuition would beg the fact that the conversions could be made. Using a conversion website (sources will be listed below) I found that 1 gallon of gasoline contains 131760000 joules of energy. 1 joule comes out to be .239 calories. By doing the math it is shown that 1 gallon of gasoline contains 31477853.69 calories. Just as a frame of reference, that is the same as eating 149,894.5 Hershey Bars.

     Now, we presumably want the best MPG possible so for that we need to find the fuel efficient running speed for a human. A small study done by the University of Wisconsin-Madison (again all source below) determined that for males the most efficient running speed is approximately 8.3 miles per hour (3.7m/s).  Taking this into account we can determine how many calories would be burned is the average male were running at this speed. According to the CDC the average U.S. male is 195 pounds. A 195 pound person running at 8.3 miles per hour would burn approximately 1128.5 calories per hour (This is the last time I'll say it, sources below).

     So if I have crunched the numbers correctly, and I'm hoping I did, then I have found the answer to my question. If the average U.S. male were running non-stop at the most efficient speed of 8.3 mph and could use gasoline as fuel he could run 27,893.53 miles on one gallon of gasoline. Almost 28,000 mpg!!! Now sorry to say this number probably shouldn't be that high. I did not include the basal metabolic rate which every human has just to perform the basic life functions. Also, I challenge you to find an 27,893.53 mile long perfectly flat place for someone to run. Running uphill would burn more calories and hence lower the average mpg. Even though this number is just a rough estimate it shows how efficient human running is.

Sources:

http://www.zoology.wisc.edu/faculty/ste/finalpublishedpdf.pd

http://www.cdc.gov/nchs/fastats/body-measurements.htm

http://cdn.builtlean.com/wp-content/uploads/2013/06/Bmi-chart-big.jpg

http://calorielab.com/burned/

http://www.calorieking.com/foods/calories-in-chocolate-bar-milk_f-ZmlkPTU4NDc1.html

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