The link in the thread appears broken, but after my own Google search I do stand corrected good sir! Thanks for pointing me in the right direction.
FYI:
Coasting in Neutral or Gear to Save Gas - Coasting and Fuel Economy
The challenge I would have to this, however, is it assumes there is zero throttle input in both scenarios. Where the hill is not a significant grade, being in gear may actually require you to use some throttle to maintain a constant speed due to the drag the drivetrain creates, and therefore you would use some fuel, whereas coasting would likely be longer before a throttle input is required. Which one is more, I don't know, but I'm sure someone out there has tested it.
I, personally, get the best fuel economy when there's no traffic, because I'm not having to adjust speed because of the person in front's inability to maintain a constant speed, and also I can allow the car's speed to fluctuate a little with the undulations (letting off the accelerator early over the crest of a hill, or allowing it to go a little over the speed limit down a hill when there's an uphill coming, etc)
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