I had a commute similar to the OP's, and I averaged 28.5 to 29 mpg when driving as a zombie...and 26.5 to 27 mpg when alive.
I found, when my mileage began dropping over the last 7 years, that the MAF was going bad, the coils were going bad, or winter's crappy fuel had arrived.
So, one needs to keep their mkv firing well to achieve top running mpg.
All that will effect the mileage are going to be:
plugs
coils
failing maf or O2 sensor
fouled injectors
running rich - vcds group 33
gummed up intake ports
old oil
using 5w when 0w oil is better for winter mileage
fueling not running optimally...etc.