This is exactly what I do, but I use fueleconomy.gov
This is exactly what I do, but I use fueleconomy.govI signed up too. Great looking site. I've been logging my mileage since 2005 on another site, but thought I'd join that one as well.
For people who don't log but are starting, the easiest thing to do is get a receipt every time you get gas and write the mileage at the top of it. It took me a bit of getting use to, but after a month or 2 it becomes second nature.