Really all depends too how the air glides over the car, I would say wash and wax your car, that will give you about 1-2mpg, actual number too. The DIC isn't always right either, add up your miles on a full tank and divide it by 12, that will give you actual average mpg. Are you using air conditioning during this time?
Mike I would assume that it is all around hwy and city seeing as it is DIC reading and the car's computer knows no difference.
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