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Old 07-03-2009, 08:32 AM   #5 (permalink)
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Join Date: May 2009
Location: Charlotte NC / York SC
Posts: 728

05 DMax - '05 Chevrolet 2500HD
90 day: 18.48 mpg (US)
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Gasoline engines are at their peak efficiency at wide open throttle.
If the factory tranny kept it loaded and floored at 70mph then it was on its most efficient spot of the curve.
Changing the gearing pulled it off peak. I wonder what the MPGs at a higher speed would've been?
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