This week’s Week in Numbers requires a bit of an introduction. One of my new favorite blogs is Ecomodder , a site all about modifying your car to make it more efficient and environmentally friendly. This week Ben wrote an article about gas mileage monitors that are, for the most part, easy to install.
The MPGUINO is an entirely DIY monitor that you’ll have to sodder and wire into your car, it’s what Ben uses and the only option for cars made before 1996 because the rest of the gauges rely on hooking into the ODB-II system  (On-Board Diagnostic System).
It’s also one of the cheapest at between $30-$40 plus the tools needed to install it.
The ScanGauge II 3-in-1 Compact Multifunction Vehicle Computer  runs a little pricier at around $160 but is one of the most popular gauges and one of the easiest to install (hooks into the ODB-II port underneath the dash, which means you have to have a ODB-II car). In addition to offering up gauge-type information, it lets you check engine codes and helps with other diagnostic function.
- Programmable 3-in-1 automotive trip computer, diagnostic scan tool, and up to 37 digital gauges in one (vehicle dependent)
- Watch fuel consumption, cost-per-mile, coolant temperature, engine speed, horsepower, and much more in real time
- Works on all 1996 or newer OBDII cars, including gas, diesel, propane and hybrid vehicles
- Checks for Diagnostic Trouble Codes (DTCs), clears the codes, and can turn off the “Check Engine” light
The PLX Kiwi , at a pricier three hundred bones that offers more than a gauge. It can monitor your driving behavior and “teach” you how to become a better driver through ratings and suggestions.
- Named after the green fruit, the Kiwi is a green driving device that helps users monitor their driving behavior and increase fuel efficiency. With Kiwi users can save up to 33% on their fuel consumption while also reducing their carbon footprint by 2 tons per year!
- Monitors driving behavoir over four parameters Smoothness, Drag, Acceleration, Deceleration. Also comes equiped with an Instantaneous MPG readout
- Drive Green mode is a series of lessons designed to optimize user’s driving behavoir
- Check engine feature can diagnose and fix engine code errors
- Compatible with all vehicles 1996+ including hybrids.
The MSD Ignition 13100 DashHawk Vehicle Information Display  is another unit that runs around three hundred bucks and looks crazy slick, though it’s not clear what you get (that you would need) over the ScanGauge II besides a more polished looking unit (and backlighting!).
4 Ways to Add a Gas Mileage Display to Any Car  [EcoModder Blog]