Low is subjective.

1. fill up tank with gasoline.
2. look at odometer, note miles.
3.drive till needing more fuel. you don't have to do this all at once.
4. fill up tank with gasoline, note amount of gallons of fuel pumped.
5.look at odometer. note miles.
6.subtract fisrt miles number from this second miles number to obtain
difference.(miles driven)
7.divide number of miles driven by number of gallons pumped to derive miles
per gallon. (MPG)
8.multiply MPG by capacity of fuel tank in gallons. Check your owners manual
for tank capacity.

Hard to respond when you say nothing about how and where you are
driving.

Around town I don't expect to get more then a little over 200 on a
tank.  On a trip I can usually go about 300.  When I check the mpg
it's usually between 13 - 15 for city/commuting and maybe 20 on a
trip.  For as underpowered as it is, the mileage isn't very good but
it's about the same as all the rest.