Hi,
There is no etiquette as such. Common sense and decency which unfortunately is lacking in today's society should be the only consideration. Think of it this way, you need to fill up your petrol/Diesel car and at the petrol station there is only one pump that gives you either petrol or diesel but not both at the same time. So how would you deal with that currently?
You would wait in an orderly queue patiently (usually), what you wouldn't do is:-
a. Jump the queue.
b. Park in the front of pump and duck off for God knows how long, to God knows where.
c. Take an excessive amount of time to fill up
d. Park an electric car in front of the pump and when anyone challenges you say "who the duck are you the parking police".
e. Leave your car unattended with the nozzle in the car (obviously full) bigger off and leave it and return only when it's convenient for you.
I hope you get the picture.
Regards
Frank