I might as well add to this thread.
My '18 G12 get's 9 MPG in it's daily 6 mile round trip commute, but I've achieved 28 MPG on long commuted up and down the California coast (lots of ups and down roads).
ECO mode does not seem to help by any measurable means, but it's such a depressing feature. The vehicle's under performance for absolutely no gain (in MPG), instantly removes the smile-per-mile.
I'd be thrilled with 12 MPG city.....really!
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