You got it, there, brillo ..... :)

Your representative sample is way too small and the experiment isn't replicated.

I reckon that readings (hand calculated) taken over several tanks would give you a pretty good idea of your car's fuel economy.

Yes.

Your sample set is too small for you to get conclusive evidence.

-alex

As others have said, your sample is way to small to be meaningful. I keep a log book and record every fill up and the mileage, and I can report a low of about 26 mpg and a high of 33, which seems to be pretty typical. I'm a mature driver who likes to wind it out every now and then when it's safe to do so.

BTW, my car is 100% stock.