danaeris | An Interesting Discovery

Doing research for my future car purchase, I was disturbed to discover discrepancies in the mpg provided for any given vehicle on different websites. The units were supposedly the same, but the numbers were different.

Now I know why.

In the 1980s, an EPA study found that drivers were typically achieving lower fuel economy than predicted by EPA laboratory tests. As a result, EPA required the laboratory-derived city and highway MPG estimates posted on the labels of new vehicles to be adjusted downward by 10 percent for city estimates and by 22 percent for highway estimates to better reflect the MPG real-world drivers can expect.
— US Fuel Economy page

When I adjust for those percentages, Canadian PR and US PR line up.