When I bought the car and filled it, the trip computer said 270 miles and 20 MPG.
I didn't reset it... still don't know how to reset it tbh hehe - but I drove home at 50-60mph for 220 miles.
By the time I got it home it was saying 290 miles range at 38.4mpg and the gauge was at around 60%
I don't think I was driving it right
It'll drop a lot faster now I'm driving to work round town but I think I could have easily got 400+ out of the tank if the journey was long enough at 50mph.
I wouldn't have survived 8 hours in the car on one journey but it's theoretical.