Hypermiling

Thinking about getting one of these gauges:

Commercial

I think it sounds like the Scan Gauge II can show PID codes whereas nothing about the e seems to discuss that capability.

• Scan Gauge e
• Scan Gauge II
• Adding into a Honda Insight
• Comparison
• Ultragauge

Arduino

Opengauge

• MPGuino
• Obduino
• wiki
• opengauge code site (they do obduio and mpgduino)
• Kickstarter for OBD networks

CAN duino

I'm not entirely sure about this but I think CAN BUS has something to do with control (like if you wanted an Arduino cruise control.

• Canbus shield
• CAN BUS

Sparkfun

• OBD-II UART
• Tutorial

Mileage

I've often thought efficiency is an interesting idea. You have to be precise about the numerator and denominator though, what are you measuring? Is it vehicle miles/gallon, or person miles/gallon. For instance, hauling 8 people in a van may have poor vehicle miles/gallon, but actually a high person-miles/gallon ratio compared to driving multiple, separate vehicles required for a quantity of people to travel the same distance. xkcd's mpg what-if has an interesting take on how mpg (vehicle-mpg or person-mpg) is really an area term.