As already stated unless you can drop off the extra weight at the bottom of the Hill itadding weight will always be a loss ... In my opinion
there might be more to the story if you were able to Balance the car and see improvement a 50/50 ratio of weight distributed consistent throughout front to back left to right will result in better performance so that should translate to effiiencey.
quick example is pushing weight to pulling it relocating your car battery from the front of your car to the trunk will result in performance gains that is why it is an old racers must do list when hot rodding a car. perfect balance and weight transfer in acceleration will result in gains everytime compared to a stock setup on the racetrack.
Sorry I am not a numbers/ Math guy or even a scientific theory person I understand what I see.
So ask the guy in the 5500 lbs truck trying to climb the hill if fuel mileage has increased with weight
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2012 Chevrolet Traverse *active*
2002 Oldsmobile Alero GLS *active*
2002 S10 2wd p/u 139,000mi. *active*
1975 Corvette Stingray *active*
1994 Camaro Z28 Convertible 149k *Sold 2013*
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1995 Tahoe LT 250k *Sold 2011*
