Well, it’s finally happened: Americans are starting to use less gasoline. It took a weakened economy and record oil prices — crude hit an all-time high of $103.95 a barrel Monday — but in the past six weeks, U.S. gasoline consumption has fallen by an average 1.1 percent from 2007 levels, the most sustained drop in at least 16 years (excepting the dropoff that followed Hurricane Katrina). As Americans move to mitigate their gas-pump pain by seeking out more fuel-efficient cars, migrating into walkable neighborhoods, and riding public transit, analysts are suggesting that reduced gasoline use could be a long-term trend.