GAUGE, FUEL ECONOMY, 2", RPM/MPH/INST & AVG MPG, DIGITAL, OBDII, ECOMETER IIThe Single Largest Contributing Factor To Fuel Economy On Your Vehicle Is The" Loose Nut Behind The Wheel" . Driver Input Affects The Amount Of Fuel You Use More Than Anything Else. The Ecometer By Autometer Is A Simple, Plug And Play Device That Connects To Your Vehicles Obdii Port And Allows For Instantaneous Monitoring Of The Exact Fuel Economy Of Your Vehicle. So Much More Than A Simple Vacuum Gauge, The Ecometer Monitors A Huge Range Of Engine