The subject of gas gauge comes up from time to time.
The analog gauge is to give you an "idea" of how much gas is in the tank.
The digital gauge is a bit more accurate, but there is no such thing as miles per bars. Like most gas gauges, in the upper range, you get more miles per bar, in the low range less.
The suggestion to zero a trip meter (either A or B) at each gas fill is the best idea. Get to know your :spyder2: and drive accordingly. You will soon know how many miles "your" :ani29: will get per tank, which also depends on "your" driving habits.
When the refill light goes on, its time to start looking for more gas.
Last, refill to the same level each time. I always come up to the filler ring, stop, let it settle for a second or two, come up to the ring a second time, and STOP.
We usually get about 150 miles to refill light on the 998 and 200 on the 1330. I have done 180 on the 998, it showed empty, and took 5.2 gallons to refill that one time.
And of course the usual: WARNING, WARNING, WARNING, your gas mileage may vary.
Excessive wind resistance and excessive speed will both suck up your mpg--if that matters to you.