A fuel consumption gauge is needed, if you want to measure the fuel consumption that your car has been consumed in daily life. Some of the newer vehicles have the display on the “real time” data on a dashboard display, but not with those old cars.

In order to know the fuel consumption, you might have to make your very own easy-to-read miles per gallon (MPG) display. For your information, this low-cost project is to use an inexpensive Atmel 8515 AVR microcontroller to collect real-time vehicle speed and air-flow data, especially from an engine by using the J1850 VPW bit-serial bus. After that, it displays that information as a fuel consumption rate in miles per gallon (MPG) with the help of an “analog display”, where it makes from an off-the-shelf electronic tachometer with a modified meter face-plate.

Basically, the ATmega8515 microcontroller is collecting vehicle speed and airflow data from the vehicle’s engine computer using the SAE J1850 VPW bit-serial bus. In the other hand, a modified off-the-shelf electronic tachometer is being used as an analog display, where it shows the consumption rate in miles per gallon.

You don’t need any special automotive bus interface chips for this project.