I go 300 miles per tank when I know there is gas within 25 miles of
there.   I have gone 300+ and never seen over 14 gallons pumped, so I guess
that is reasonable...I try to fill at around 300 miles max...   Out west
here and living in a semi- rural area, having decent range is rather
important or you end up taking on fuel all the time, in order to make some
of the destinations where I often go....You might have the fuel to get
there, but there is no station there....or you might want to arrive or
depart when the station is closed...many rural stations don't have those
auto card readers always on pumps...and Oregon is weird... I routinely do a
100 mile round trip windsurfing 'commute' to one of my favorite spots on
the Eastern Columbia River....There is no station after one that is only 8
miles up the road...The closest one from the windsurfing venue is another
35 miles beyond it...So I keep an eye on my odo...my gas gauge is rather
vague depending on the attitude of the van....

   My Moto only has about 140 miles of range and that is very tedious to
manage...The newest vehicle in my stable holds 27  gallons of fuel, but it
sucks it up at ~15mpg....darned automatic..