I agree that a 1/4 mpg isn't much. It's been stated that the difference is a 1/2 mpg, but that isn't really the point of the conversation. It's definitely more of friendly discussion. However, saying we just have to assume it's there because of mileage is not necessarily true. In an industry, world for that matter, where designs are driven by the mighty dollar an extra piece of plastic wouldn't be added for no reason. There is a gm published video showing the results of the dam and it's quite amazing. This is definitely included on the vehicle to help meet the demands of the federal gov for mileage.
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