I don't know what it is - I went from a Ford Taurus to a BMW. All of a sudden I felt the irresistible urge to ride on anyone's bumper in the left lane. I actually bought a Peach Pass I didn't really need just so on my infrequent trips to Atlanta, I could pass those slow mofos in the left lane. I became expert on passing on the right when that slow SOB wouldn't get out of the way, even if it meant using the shoulder. If they didn't want you to use it they wouldn't have put it there.
Don't really know what it is, except part of The Force.