I've had the scangauge II for over a year. It is very cool, especially in the beginning. You have to remember to reset it after each tank fillup. But like mentioned already, it didn't teach me anything I didn't know about mpg, but it the other info like
battery voltage, temps are helpful when towing. Well worth the money for a fun gadget. Also it will decode any engine codes as well, then you don't have to rent/buy a device for that.