Since August when I bought a new type Prius, I
drove it about 3,500 km for 3.5 months through today. The average
fuel mileage is over 16 km per litter.
As Prius starts form 0 speed with its electric engine which has big torque at lower speed, I can enjoy the comfort that I can leave other vehicles behind on streets when I start from stop sign at road cross without having any intention to go fast. As the battery weight was decreased by 200 kg and also its size was reduced, the new Prius has much more luggage space than the original one and other merits too. The new Prius can go on express way on the same speed as of gasoline engined compact vehicles. On sharp upward slope, sometimes Prius can climb faster than them as its power is supplied both gasoline and electric engines. In short it can go equally or more with gasoline engined cars.
I have a bad habit from old days by keeping a heavy golf bag in my car's trunk and also I put on air conditioner throughout year to keep 25 degrees in cabin. Futhermore it has a full automatic transmission. So the above said fuel mileage shows that its fuel economy is about two times better than the ordinary five passenger compact sedan.
As I have been accustomed to drive it, I have understood a scheme of hybrid vehilces to some extent.
The first point is that its gasoline engine is automatically stopped when the vehicle stops at stop signal or congestion on streets. This scheme is one of the best measures to economize fuel consumption. The restart from 0 speed is powered by its electric motor and the gasoline engine starts automatically after the vehicle gets a speed of over 10 km/h.iYears ago, to shut off engines when the vehicles stopped on streets is tried as one of the anti-pollution measures. But when the vehicles restart, their engines consume much fuels. So it was not much effective and such vehicles faded away.) Sometimes in the center of Metropolis, traffic on streets stops for longer time than moving. Therefore this scheme is very effective.
The second point is that when the car is running on flat road, driven by gasoline engine, its batteries are charged with electricity (In the other words, when the gasoline engine generates powers much more the necessity for running on flat roads, the surplus power is saved in batteries as electricity.) Because of this scheme, Prius needs not to get power supply for the outside power resources.
Even when you climb up upward slope, Prius saves electricity in its batteries althogh it is a bit against the common sense. Because people are apt to push accelerator a little harder than getting the necessary power with the result that the generated excess power is saved in batteries. When you go downward, electric engine is changed to a generator and is used as regeneration brakes.
The electricity thus saved in batteries is used for driving a vehicle and make it possible to save fuels.
As this scheme is no relation with weight and size of vehicles, it can be applied to vehicles of any size, any kind of vehicles, cars or trucks, and any engine, gasoline or Diesel. Therefore it is not difficult to increase fuel mileage two times or more on any vehicle. Although city driving is better fuel mileage than highway driving according to the officially registered mileage, my Prius has better mileage on highway than on city streets.
I presume this scheme is much more effective for saving fuels on vehicles powered by bigger engines ( I am a bit afraid I am wrong as I am not professional.) So manufacturers in North America or in Europe of big powerful vehicles should adopt the said scheme first.
Already Toyota announced to have middle and large size hybrid vehicles in near future. Furthermore, President Cho of Toyota Motor said in U.S.A. a few days ago that a half of vehicles will become hybrid vehicles in near future.