I have. 125 honda 2014 model. For last 3 years its MILEAGE has been exactly 55 km per liter if i drive it on long road with less to no brakes or aggressive acceleration at 60-70 kmph speed.
If i drive harshly then it gives exactly 30kmph on long and in city it get 40-45 and sometimes 30 because i drive as harsh as throttle can get. And brakes can be pressed. I use big rear tyre and good braking grips by decreasing air pressure to front tyre 20 psi and rear 30. Single rider mostly. And my bike has driven 90k + kilometers on odometer. Hope it helps you.
Mechanic can do wonders.
When i was in lahore, bad petrol, less amount by cheating and bad mechanics made my mileage to 15 km pl.
I twice on separate occasions drove my bike 28 km with half liter petrol. Twice. And i always check my mileage once or twice a year every year.