"hand calculated" figures can be inaccurate (vary from the TCH's figures) the because the amount of fuel used will vary from tank to tank because of the pump shut-off variations.

True, but over time with many tank fillings, the error is small by hand calculating. That's why I'm not paying much attention yet to the milages on the data base as most are at 1 tank and on one tank you could be off by 1 or 2 mpg's with just a couple of squeezes of the pump. Also on that first tank you don't really know if it was full when the dealer gave you the car unless you went out and immediately topped off the car. That alone, even over 2700 miles could account for getting me over 38.

I calculated the other night that my average over 2700 miles would go up by almost 0.5 mpg (getting me over 38) with just 1 less gallon of gas. The pursuit of the "ultimate" number is not really profitable, simply fun.