[Palm]

If you were to drive to a location and back the same way, wouldn't a heavier car = better fuel economy? Of course this is provided you don't brake or use engine braking. My thinking behind this is that you use more engine power on the uphills which boosts engine efficiency and reduces pumping losses etc. Because of the higher weight you also have a correspondingly higher kinetic energy at the top of the hill enabling you to coast in neutral further than with lower weight.

Is there some merit behind this way of thinking?

Also, instead of the technique used by some to drop speed on the uphills and gain it on the downslope, wouldn't it make sense to use the throttle generously on the uphill and then also coast downhill of course? Yet again for the increased efficiency.