By thinking about the fuel efficiency of your diesel as somehow being relevant to the pollution zones shows you have made an error that is pretty commonplace.

By thinking about the fuel efficiency of your diesel as somehow being relevant to the pollution zones shows you have made an error that is pretty commonplace. One shouldn’t confuse fuel efficiency with fewer emissions. Motorcycles for example are very fuel efficient for getting a person or two around without a lot of stuff as compared to a car, but they cause way more pollution per mile (which makes it even worse than measuring by per gallon, exactly because they are so fuel efficient, making it strikingly bad because to achieve worse emissions per mile, their emissions have to be truly extraordinarily bad). (Yes, other commenter who wants to retort that the type of motorcycle matters, it’s true that it does. This is a general point about internal combustion engines where some motorcycles are being used as an example.)