Well, the way i measure is RESERVE to RESERVE method....
I fill up my bike tank (full) and note down the reading from ODO meter. And when it his RESERVE i note down the reading again....
Suppose while filling bike's meter reading was 1000km. After using/driving and when it hit RESERVE it's reading is 1350km...
Final reading - initial reading
= 1350km - 1000
= 350km
My bike (CG125) has 10 litres fuel capacity and 2 litres is for RESERVE. 8 litres!
350km/8 litres = 43.75Km/L 
@faiz.aslam.121
Bhai! It won't harm engine
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