@valerian, you need to do an actual mpg calculation with your next fill up. If you have a large difference in your actual calculation and the car's calculation. You can make some changes to the settings, that will bring the two to more closely match.
@maydk I agree with you, I have to check the accuracy of the gauge.
When I bought the car in 2018 I checked with Gasbuddy and the displayed mileage was under estimateur by 5%. It may have changed with the car aging.
Do you think about an adjustment using the Forscan?
No need to use Forscan. Take a look at this post about MPG Adjust. @metroplex made a post starting @ #14. Gives you nice simple way to make the adjustment, just using the buttons on the steering wheel.