NORMAN — Darrell Glenn of Norman checked into selling his 2003 Toyota Sequoia , hoping he could turn around and buy a smaller car with better gas mileage. He quickly found out he owed more on the Toyota than he would get by selling it.

Glenn and his wife try to conserve fuel by doing errands and shopping only two days a week.

Every week, she makes "a meticulous list of what I need, where I need to go an...