[MetroMPG]

The SG is a better tool, hands down. More functions, less expensive.

The MID's advantage is that it can be used on non-OBD2 equipped vehicles. The SG only works on OBD2.

Theoretically the MID can be installed in any vehicle with a VSS (Vehicle Speed Sensor) and fuel injection. It was initially developed to give Prius owners the ability to measure MPG beyond the 99.9 mpg limit of the OEM display (and a few other measurements not on that display).