I agree 15 to 18 mpg is unacceptable. I'm getting 15 t0 16 at 70mph. 18 at 60mph. I don't like to drive under 60 mph on an Interstate highway.
Mercedes can't find anything wrong and tells me that mpg is not guaranteed.
Are you doing the calculation by hand...a friend of mine was getting the same MPGs...he only used the onboard computer....turns out they are NOT exact....here he thought he was getting 17-18 and he was closer to 20mpgs...
and remember your speedometer is off by about 3 MPH..if you do 70 by the needle you are actually doing 66-67.mph
Just trying to help you find that extra mileage...
and what tire pressure you at?
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