Nozzle sizes are:
unleaded 13/16"
auto diesel 15/16"
hi-flo diesel 1 3/16"
That said some vehicles have a flap that requires the exact size nozzle to open the door. For instance I have a 2020 Wrangle diesel, even though the gas nozzle is smaller it won't open the flap. I found this because I needed to put diesel in it with a fuel jug and the flap wouldn't open. there is a special adapter you use with a fuel jug that doesn't have a 15/16" nozzle. My wife has a Mecedes GLK diesel,,,, no flap or restriction,,,, you can use the hi-flo nozzle to fill up.