A few months ago I started an experiment. Every time I filled my 2004 Subaru Outback with 87 gasoline, I recorded the gallons at the tank and reset my odometer. The next time I refueled, I repeated the process. My theory is that EPA-rated mpg for cars is not indicative of real-world driving and as a consequence is much higher than actual mpg. I put that theory to the test and here are my results:
(note: I wrote the above paragraph before doing these calculations to prevent a perceived bias in my theory)
Code:
Gallons of 87 gasoline Miles travelled Mpg
13.937 348.3 25.0
13.902 279.4 20.1
14.542 338.9 23.3
10.718 292.5 27.3
14.650 372.7 25.4
13.908 296.8 21.3
13.543 280.1 20.7
Average MPG = 23.3 (9.9 KmPL)
According to
this site, my Subaru Outback (second one down on that list) is rated by the US EPA to have mpg's of 19 (city) and 25 (highway) and 21 (combined). Since my driving consists of both highway and city miles I took the average of city and highway miles just as another benchmark, 23. Also notice that one user has posted results for this car as 22.7.
So from my experiment it is clear to see that my theory was incorrect. My average of 23.3 mpg is much higher than the city and combined rated mpg's. Furthermore, my average is only 1.7 miles below the EPA listing of 25 mpg highway. Also note that the EPA average for city and highway miles is only 0.3 from my results.
I attribute these differences to the fact that my sampling period was during the warmer months of the year, which gives a slightly better fuel economy I believe. My 5-speed habits may come into play as well.
All in all, a fun and informative experiment!
Anyone care to share their results? Or even just comment on mine?
