I downloaded the free version of the Gas Cubby iPhone app as a way to track my mpg per tank. It seems like a good app. It allows me to track gallon price, fill-up price, mpg per fill and log maintenance visits. I'm thinking about getting the paid version, but I wondered if anyone has tried the paid version or other iOS mpg apps. I'm sure Android has some good apps like this, too, but sometimes apps aren't available on both platforms. I like that after I enter in the gallons purchased, gallon price and odometer reading the app automatically does the mpg math. It saves me from breaking out the calculator.