I've got mixed results about the fuel tank capacity on the pre-LCI EU-models. Some say that the basic fuel tank was actually only 30L and the 42L tank was an option called "S1AG Larger Fuel Tank".
Is this true or not? Here's some random google hits but additionally at the time at least one test drive article said the same (in Finnish language)?
https://motoreu.com/bmw-i8-mpg-fuel-...ications-36407
https://www.carplanner.eu/catalogue/...eadmore/26192/