HI
would you please send me the details of the VEHICLE MILEAGE TESTER FOR NEW VEHICLES
like circuit diagram,source code and all please as early as possible.

i think its you do by vehicle's drive wheels are placed on a machine called a dynamometer then run vehicle ad usual method (here the dynamometer rollers will rotate by vehicle tyre , instead of moving front) and the calculation is based on energy required to move the rollers can be adjusted to account for wind resistance and the vehicle's weight ....

i dont think , any source code or circuit diagram is required for it