why do you need to run it empty to see economy? just run it till the fuel light comes on. fill it up, record your k's. then its KM's travelled/ liters used for Km's per liter. Or go (liters used / kms travelled) x 100 to get liters per 100KM
If you then wanted to find out how far you would get until it stopped just subtract the amount of fuel put in from your tank size to work out how much you had left then then multiply it by your km per liter result then add it to your trip meter reading
Example:
travelled 570km
fuel added till it clicks out 59L
570/59=9.66KM/L
(59/570)x100= 10.35L/100KM
tank size 76L
76-59= 7L remaining
7x9.66= 67.62km until empty
total range
570+67.62= 637.62km
hope that helps but if your totally set on running the tank dry you should be right youll just have to hand prime the fuel back up to the filter using the primer on top of the filter assembly. I also wouldnt make a habit of it as when you run to empty itll be picking up all the crud out of the bottom of the tank and i also imagine you'd get cavitation in your fuel pump as it starts to suck air which couldnt be good.
personally id just do the maths