Here is my contribution to this topic:
N704_FCR_MPG-2.pdf
The above file shows extremely accurate records I've kept since I bought my Mk3 in March 2012 until my last re-fueling on 27 December 2014. As you can see my average MPG over 1 3/4 years is 26.29 mpg over 9,595.49 miles.
It is also interesting that my best results of 30.31 mpg and 30.67 mpg were obtained, as some readers have pointed out, when the weather was warm. I should also point out that my best milages were obtained on long motorway runs all within the statutory speed limits (of course!). It is also worth noting that my worst result, 21.78 mpg was in December last year.
To sum up, I am very pleased with these results.
Pepe