Thanks for the reply.
I understand mileage will vary depending on driving style which is why I'm more interested in precisely how much fuel is left in the tank when the gauge reaches E. The manual says "the gauge indicates an approximate fuel level in the tank" and "There will be a small reserve in the tank when the fuel gauge reaches E".
I'm just curious if a 2.5 gallon reserve is typical for the newer Zs so I know what I have to work with.