I have been tracking my 08 Touring mpg via spreadsheet since April. My question is actually in reference to the fuel bladder and mpg because I wonder if I'm filling my Pri enough to get an accurate measure of MPG on a spreadsheet. Today, for example, I filled at the same Sam's club I always do and filled 1 click (as I always do) beyond the auto-click. My MFD read 42.8 mpg but my spreadsheet indicates 48.2. Granted the spreadsheet doesn't always indicate better MPG. Considering the fuel bladder variables, how do I really know what my MPG is?