[bestclimb]

The more efficient the car the less hypermiling or slowing down pays.

Starting at 20 mpg increasing mileage by 25% goes to 25mpg.
For 1000 miles you go from 50 gallons to 40 gallons. You save 10 gallons.

Start at 40 mpg an increase of 25% gets you to 50mpg
for 1000 miles you go from 25 gallons to 20 gallons. You save 5 gallons.

One of the great reasons to ecomod a car or replace a vehicle with one significantly more efficient is that you can get better mileage without having to slow down.

Your point that people don't think about their driving remains valid. However to assume that every hybrid driver is oblivious to the savings and how they drive is likely false. It is very likely that some have done a cost benefit analysis and came up with the answer that their time is worth more than the fuel they could save.

Were I to find a very efficient car to commute in (1st gen insight for example) I would likely drive significantly faster than I do now as the money saved gets smaller and the time lost (5 min per trip) stays the same.