Here in the Netherlands, we'd translate 31mpg to "1 per 11". One can drive 11km on 1L of fuel. 1 per 11 is a joke. It's associated with heavy petrol cars from the 80s and 90s, before anybody even attempted efficiency.

Even my 15 year old diesel car had an efficiency of 1/22. Adjust you driving style and I'd get 1/25. Range: 1000km, with an ordinary sized tank.

It seems Americans haven't even started with efficiency, quite likely because there was no pressure to do so due to low fuel prices. Not in their homes, not in their cars, not anywhere.