Regular gasoline prices in the Metro Detroit area have drifted down over the last week, from about $3.00/gal to pre-Katrina prices in the neighborhood of $2.60/gal.
What I found amazing was that even when gasoline was selling for $3.15/gal, I still saw lots of people driving their Dodge Durangos, Ford Expeditions, and Chevrolet Avalanches. With no passengers. At 80mph, get the hell out of the way.
For all of the whining that people were doing on the evening news, about how they weren't going to be able to buy as many Christmas presents this year, no one seemed to change their driving habits much. Just slowing down from 75mph to 65mph can give a 10% boost in fuel economy, I have heard*, but people refused to do even that.
Consider: at 65mph, a 15 mile trip will take ~14 minutes. At 75mph, the 15 miles takes 12 minutes.
Would you notice if your drive to work was 2 minutes longer? Most people wouldn't. There is probably at least that much variation day to day based on irregular traffic flow, and variations in when you reach traffic signals.
On the other hand, getting 10% better fuel economy on your morning commute probably isn't that impressive for most people. Assuming 15mpg (the average full-size SUV or maybe a late 90's Chevrolet Impala SS), the difference between 75mph and 65mph might be 0.10 gal, or $0.32 (@ $3.15/gal). Two trips a day for a work-week, and you save one gallon of gas.
20 minutes a week, or $3.15? Which would you rather have?
*Wind resistance increases exponentially with speed.