I drove down to LA and back this last week and got 13.77 MPG in my 2005 E350 chateau with V10. I set the cruise control at around 65-67. I didn't expect it to be that "good" but I was pleasantly surprised to get that kind of mileage. Van only had me and my son in it.
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2005 E350 Chateau - V10 - Agile Offroad 4x4
2012 CTS-V Wagon - For the baby...