This is pretty cool, this UK website rates cars based on CO2
output per kilometer.
We've teamed-up with What Car? to make it easy to find out which top ten
new cars have the lowest CO2 in their class. We have used What Car?'s classification
system to define which class (for example supermini, small family, executive)
a car is in, to make it easier to find the type of car you are looking for.
The aim of this ranking system is not to recommend specific models but to give
you information that can help you make a CO2-informed decision. You can refine
your search by fuel and gearbox types, and to make life even simpler, we've
colour-coded each entry to reflect the Fuel Economy Label it's like the
one you get on fridges and washing machines.