February 17, 2015

Diesel versus Gas Prices

Lately I've been  seeing a very steep premium for diesel fuel prices over the cost of regular gasoline.    One of the pricier stations had regular for $2.25 and diesel for $2.95.   Thats a 31% premium.   Of course thats just one example.

I found historical prices from the EIA .    The most recent numbers as of Feb 2nd (as I write this) says that the national average for gas is $1.98  and $2.86 for diesel.     Thats a hefty 44% premium for diesel.   I the EIA data and pulled out just the prices from the first week of each month.   Below is the trend showing the difference in prices for diesel over gasoline :

The current difference is abnormally high.   You can see the large spike for the most recent data which is way off the chart compared to normal.   Usually the % difference is less than 20% but now its hit over 40%.   

You can also see that it varies seasonally.     I plotted monthly prices for a few years 1995 to 2000 to see how the difference varies month to month. 

Generally diesel is around 5-10% higher than gas in the winter and then drops to ~5% cheaper

Overall diesel averages about 6% higher than gasoline over the long run.     The mean and median are both 6%.


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