Interestingly, I found that the good mileage is significantly affected by the driving style. Prius engineers had used the so-called "Hybrid System Indicator" to persuade drivers to save fuel unconsciously. Therefore the MPG is overrated. I tried the ETK856 hybrid and the BeamNG-official 856, in the same course with the same driving style, the MPG only increased about 1/3. Not as high as Prius compared to other cars.