The short answer:
S is for low speeds with quick pickup.
S is not economical. Thats why the
eco light is off.
Use B when you're climbing down steep hills and needs
to slow down without overheating the brakes.
The long answer:
- Brake (B)A mode selectable on some Toyota models. In non-hybrid cars, this
mode lets the engine do compression braking, also known as engine braking,
typically when encountering a steep downhill. Instead of engaging the brakes,
the engine in a non-hybrid car switches to a lower gear and slows down the
spinning tires. The engine holds the car back, instead of the brakes slowing it
down. For hybrid cars, this mode converts the electric motor into a generator
for the battery. It is not the same as downshifting in a non-hybrid car, but it
has the same effect in slowing the car without using the brakes. GM called this
HR (hill retarder) and GR (grade retarder) in the 1950s.
- Second (2 or S)This mode limits the transmission to the first two gear
ratios, or locks the transmission in second gear on Ford, Kia, and Honda models.
This can be used to drive in adverse conditions such as snow and ice, as well
as climbing or going down hills in the winter time. Some vehicles will
automatically shift up out of second gear in this mode if a certain RPM range is
reached in order to prevent engine damage. Although traditionally considered
second gear, there are other names used. Chrysler models
with a three-speed automatic since the late 1980s have called this gear 3
while using the traditional names for Drive and Low.
- S or SportThis is commonly described as 'Sport mode'. It operates in an
identical manner as 'D' mode, except that the upshifts change much higher up the
engine's rev range. This has the effect on maximising all the available engine
output, and therefore enhances the performance of the vehicle, particularly
during acceleration. This mode will also downchange much higher up the rev range
compared to 'D' mode, maximising the effects of engine
braking. This mode will have a detrimental effect on fuel economy. Hyundai
has a Norm/Power switch next to the gearshift for this purpose on the Tiburon.
GM also used S to indicate a "super" mode, being the same as the 2 position on a
Chrysler, shifting between only first and second gears.
use B or S for general driving as both are very low on fuel efficiency.