aeroBits,
One thing to remember if you are comparing the effiency of your car (in terms of mpg) with your US based college is that a UK gallon is different to a US gallon:
1 UK gallon = 4.5461 litres
1 US gallon = 3.7854 litres
Don't ask me why or how the two volume units are different, they just are!
So the odds are that your US friend is actually getting about 50.4 miles per UK gallon out of his/her Prius (which is still less than impressive fuel economy for an "environmentally friendly" car).
Apologies for the off-topic nature of this post...
