Improving the mileage of your Aprilia GPR 250 can be done in a few different ways. The most important factor is to make sure your bike is properly maintained. This includes having your bike serviced regularly, making sure the tires are properly inflated, and ensuring that the oil is changed regularly. Additionally, you can invest in a fuel-injection system to make sure your engine is running as efficiently as possible. Finally, it is important to make sure you are driving your bike in the most fuel-efficient way possible – this means avoiding hard accelerations and sudden stops.