if its automatic

You might wear out your pilet bearing, it's a $6 bearing, but you have to pull the tranny to get to it, and the ones that come with some of the new clutch kits are crap.
otherwise I don't see an advantage of keeping the engine engaged and running fast if you don't need the power, once your engine is warmed up any blow by gasses should get cooked out, along with any water, not letting an engine warm up is when you start to have problems with water in the crank case and in the exaust, the spark plugs use the head as a heat sink, so if your engine is warmed up then the plugs shouldn't foul easly, if you find that they are fouling, then go up a heat range.

ye ai forgot to add that....u can do whatever with a manual tranny, just automatics will be toast real quick with engine off coasting;)

Pilot bearing in a manual is not getting damaged when the engine is off because it is not spinning - the clutch and flywheel and input shaft to the tranny are all stopped. The only time the pilot bearing is in use is when the clutch is held in then the input shaft with the clutch disk can be turning at a different speed than the flywheel + pressure plate + engine crank. Coasting in Neutral with the engine off the flywheel and input shaft are stationary.

you're correct, at the time I was thinking about coasting with the clutch disengaged, as well as the car being in neutral so you aren't turning the main shaft of the transmition as well.

So if the engine is running, and I'm moving in neutral, and the clutch is not pressed in, then I'm ruining the pilot bearing?

No, there should be no movement on the pilot bearing under those conditions.

Let's take a quick step back: A pilot bearing is NOT the same as a clutch throw-out bearing, which is the bearing that slides along with the clutch lever up against the clutch pressure plate fingers. A pilot bearing is usually a shaft-end bearing designed to stabilize, and it is often (though not always) designed to spin as fast or slow as the engine and or transmission will normally spin.

A throw out bearing by contrast is not designed for sustained high rpm spinning, but rather only during the momentary disengagement of the clutch pressure plate when it has both axial and radial forces acting upon it. In other words, it is designed to spin only when the pressure plate is disengaged (pedal in). And because the throw-out bearing lives in the same hot dusty environment of the clutch, it is normally assumed to be a wear item that is replaced with the clutch.

It is also worth noting that many modern transmissions do not even use a pilot bearing at the end of the transmission main shaft into the flywheel.

Coasting engine off in a manual should be done in neutral, not clutch in. The clutch is designed as a momentary break between the engine and trans to allow gear shifting, not as a means of coasting.

Coasting in an automatic should be done in neutral, engine running as the transmission pump is driven off the input shaft, not the output shaft. Running the auto with the engine off means no tranny fluid is being pumped around, which means the output shaft is not being lubed, which will burn out bearings and pump crap through the rest of the system when the engine is started again.

If a Saturn overheats when idling, even if coasting at speed, then the water pump isn't pumping enough fluid through the engine. Either that or the thermostat isn't opening all the way.

Hope this helps...

well you should anticipate lights and shift it into neutral and coast up to them (should know your car good enough to be able to just take it outa gear without even having to press in the clutch.(its the point thats between acceleration and engine braking) then once you see the cross traffic lights turn yellow then push in the clutch and go to first and wait.