From the American EPA website you get the info about fuel efficiency.
If a car has an 80% option, they reduce the efficiency by 10%. (because they take the average of 100% and 80%, and consider the car is fully charged at 90%)
The two Nissan L eafs above show how vehicle manufacturers are gaming the EPA rules. The only difference between the two versions of the l eaf is that Nissan removed the option for 80% charging. This is explained in detail here - http://www.greencarreports.com/news/1096028_tesla-p85d-highlights-why-epa-range-ratings-are-inconsistent-confusing-for-electric-cars.