Lets take a scenario and play it out...
For manual cars, travelling on the expressway say PIE for
example..
Going at 90 - 100km/h, which is usually the 4th/5th gear, enage the
gear to neutral and go free wheeling...
what happens?
In detail, free wheeling enables the car to ride freely... hence
the term as the gear will not control the speed of the car as the
engine is free and not in gear. This saves fuel.
Will you lose control of your car/engine?
No, unless you switch to a very low gear, ie gear 1 or 2...
travelling from 90-100km/h and free wheel for 5 mins, your speed
should slow down to 70- 80km/h due to friction... the DANGER is
switching to a very low gear when going a fast speed, what
happens... engine brake and if you're not holding the car wheel
steady, most likely the car will start to turn as the wheels heats
up...
Will you have trouble stopping?
No, an experienced driver would just switch to a lower gear and
brake slowly... up to the driver if he wants to do both engine and
car brake... he can stop faster if not just as fast as he was if he
was engaged in a high gear.
To summarize:
Downside to free wheeling?
1) Danger of switching to a very low gear while going at a high
speed and being caught unaware ie you step on the clutch but you
move your hand to the wrong position or something hits your
hand
2) Can spoil your gear box if you do it too often and is very rough
at switching gears
3) Have to be more attentive on the road, and knowing when to
switch back to gear if the car in front slows down or
E-brakes.
Upside to free wheeling?
1) Enables you to save petrol
2) Lets your engine rest if its being running for a long time
3) Smoother ride some says
Hope this helps.
For a auto car, free wheeling can be done as well. But drivers are
generally too lazy to switch gears.
