Managed to go through the current Fuelly data (well current as of yesterday night). I pulled only cars that are specifically labelled as DSG or Manual in some way. I included only cars in the US, and found 14 Manuals and only 4 DSGs still. I broke them up a couple different ways:
All US Cars, regardless of indicated Hwy/City %:
Manual: 44.0 MPG (4.3 stddev), 58% hwy
DSG: 40.9 MPG (5.3 stddev), 50% hwy
DSG 7% worse
Removing any with <50% Indicated Hwy/City %:
Manual: 44.9 MPG (4.2 stddev), 64% hwy
DSG: 43.8 MPG (1.7 stddev), 58% hwy
DSG 2.4% worse
So, if you believe people's indicated city/hwy splits (which I'm not sure I do), my hunch that DSG owners are doing more city driving
may hold water.
Still a small sample on the DSG side. If only more Fuelly users specified! Of course, depending on which of the two ways you choose, the difference is less than my definition of "slight" from a few posts back (5%), and more than "slight" in the other case.