Please make sure that you have selected the appropriate fuel grade for your vehicle in the app's settings. You can do this by opening the app, going to the setting's panel and selecting your car. In that page, you will see a section titled Fuel Grade. You can choose between Regular, Mid-Level and Premium. You may also choose diesel if your car uses this grade of fuel, but there are limitations to which cars are supported.
If your settings are correct and you believe the costs of your trips are way off and incorrect, you may want to contact our tech support team at email@example.com.