This low-cost project measures fuel consumption in real time has won first prize from AVR 2004 Design Contest. An ATmega8515 microcontroller collects vehicle speed and airflow data from the vehicle?s engine computer using the SAE J1850 VPW bit-serial bus, which is one of the on-board diagnostic buses required by the OBD-II standard. A modified off-the-shelf electronic tachometer is used as an analog display to show the consumption rate in miles per gallon. Only a few extra components are necessary for this efficient project, including transistors, diodes, resistors, and capacitors. Special automotive bus interface chips are unnecessary. This cool project created by Bruce Lightner.