My salesman demonstrated the shift selections "S" and "B" as a design that Scion intentionally made for all or at least a lot of the braking. We were on the interstate for the test drive and he said to put it into S when I entered the exit ramp and then half way down he told me to drop it to B. I must have asked him a half dozen times if he's sure this is what it's intended for because I was always taught that you slow down with the brakes not the transmission. I haven't found anything in the manual about his described use. It's only referred to as engine braking and maximum engine braking. Uses: for increasing power going uphill, or providing engine braking downhill. Since this is a CVT and there are numerous sensors computing everything, maybe he's correct but I'm gonna call Scion to see what they say and ask the service manager at the dealership. I'll post my findings. I don't want to destroy the transmission or engine and I got it for mpg so D is probably where I should stay.