How can you get 420 miles per tank and get over 52 mpg? That don't make since. That is only 32 mpg. I get about 650 miles per tank and get about 47 mpg.
Here is a very good place to see some info and photos. Sorry, I forgot to post the link earlier.
http://www.corollaforum.com/threads/dash-cam-installed-finally.2620/
The main trick, along with a few others, is to remember, "cruise control is your friend". Obey the speed limit is another. I usually get around 655 miles per tank.