Q. What will be speed limit of Activa 5G after first Service for better millage and better engine life ?

Since the Activa is an automatic scooter, try to keep the engine as much as in low revving (only possible by smooth throttle control) at 40 to 50 kph until 500 kms. After 500kms there are no running-in as per owners manual, though suggesting to ride within the above speed limit and try to maintain it constantly and avoid hard breaking (if you know where to stop before, release the throttle and you may apply break gently until halt). Yet to complete 500kms but I get about 43-45kmpl, riding mostly on highway and so predicting city mileage would be 4-5kmpl lesser.

After first service, keeping the vehicle in the green band (40 ~ 50 kmph) will return best fuel efficiency and engine life