AnalysisWhen you go to this website you have several options for prices and you can download a year of data at a time (with a CSV as an option). The obvious choice is regular gasoline but you might want to consider things like comparing regular gas to alternative fuels like propane. For example in this case, you can see that, in general, propane also has risen in price over time but where gasoline seems to fluctuate similarly regardless of the city, propane seems to be more volatile depending on location.
Because of the shear amount of data points possible (you can get a weekly average for the last 25 years for several cities if you want), you may wish to stick to yearly values. Another option is to use some of he weekly values to talk about the dangers of extrapolation
Download the DataSite http://www.energy.gov.on.ca/en/fuel-prices/
I have also taken the liberty of downloading all of the data for gasoline (all 25 years of it) in weekly, monthly and yearly form. As well as the yearly propane data. You can get it on this Google sheet (note the tabs) or just the gas prices on Fathom
Let me know if you used this data set or if you have suggestions of what to do with it beyond this.