It's a simple illustrative paradox, but the world is complicated. I'd go with choice 5 as well. Maybe it's a world where the same number of gallons is saved (

It's a simple illustrative paradox, but the world is complicated. I'd go with choice 5 as well. Maybe it's a world where the same number of gallons is saved (per miles driven) as choice 1, but it's a world where the roads are safer.