Jodi and I keep extensive fuel-related data on our 1998 Honda Civic EX (2-door sedan). We note the mileage, fuel volume, and fuel cost for each time we stop at a gas station. This allows us to compute miles-per-gallon and cost-per-gallon as a function of time. I’ve reported on related information from my parents’ car before [1].
Over the winter break, I heard news reports indicating that we might expect high fuel prices in 2011. The data I show below supports that, but only if you perform a naive and risky linear extrapolation of the data through 2011. This is, of course, not how fuel prices trend (in the same way that stock prices do NOT always trend upward at any moment in time, not do home values only trend upward). With that caveat in mind, here is the data on our Honda Civic and fuel costs (data is a mix of California, from 2008-2009, and Texas, from 2009-2011).
Fuel price (per gallon) vs. time
The above graphic shows our recorded fuel cost (per gallon, in raw dollars) as a function of time from August, 2008 to January, 2011. We see that the highest fuel prices in the last 3 years occurred in summer, 2008, which is when the data began. For prices prior to that date (using Connecticut data), see [1]. Some data points are “anomalous” in that they are higher than neighboring points; the causes are not clear, upon re-examination of the data. This could be due to stopping at a fueling station with higher prices, or due to mis-recording of the data (swapping of two digits in a number, for instance).
We observe that current fuel prices in the winter are as high as fuel prices were in the summer of 2009. Since fuel prices are typically higher in the summer than the winter, there is some reason to expect prices to continue to rise in 2011 and peak somewhere in the summer.
Fuel Economy of the 1998 Honda Civic EX
I show in the above graphic the fuel economy of the Honda Civic, averaging over independent 30-day periods to obtain the data points (this smooths out fluctuations on a per-fueling basis). We observe that fuel economy in the Civic is better in the Spring and Fall than in the summer (the time scale is “days since 8/26/2008, so spring occurs in multiples of about 250-300 days after the start date and fall occurs in multiples of 365 days, starting about 30 days after the beginning of the graph).
The current average fuel economy is about 33 MPG over the previous 30-day period.
[1] http://steve.cooleysekula.net/blog/2008/09/12/what-a-physicist-does-on-vacation/
