Yaaay, our first advanced technique!

What is the FAS (Forced Auto Stop)?
It’s the technique were you use the situation to enable your vehicle to move continuously with the engine off. Move with the engine off? Right. You use gravity as in the case of a downhill road, pockets of quasi-vacuum left behind by trailers or big buses on the highway that will suck you in, and good old momentum.

Personally, though I do not suggest killing the engine when driving. This is way too dangerous. With the engine off, your brakes and steering capabilities are compromised and you will have to push-start your engine back on. This will take its toll on your engine and parts.

I drive a Mitsubishi Lancer with manual transmission, so I use a modified version where I have the transmission in neutral but the engine stays on. That way, brakes and steering are running 100% but the engine is idling at 700 rpms instead of my usual 1800-2000 rpms. This allows me about 10% fuel savings in terms of mpg/kpl. (This is also the technique I employ when doing the pulse and glide - more on this later.)

What cars are best for FAS?
On the outtake, I would suggest that manual transmission conventional vehicles are more suited to FAS. But hybrids have been known to do AS (Auto Stop) better.

How to do a FAS using a manual transmission vehicle (don’t do FAS on auto trannies and CVTs)

1. Evaluate the situation
   1. Do you have cars too close behind you that could bump into you if you execute a FAS? Roadrage is another danger too if you have cars behind you.
   2. Are there possible obstructions up ahead that will endanger you and your passengers if you FAS?
   3. Is there an opportunity to FAS?When the conditions are right, put the car in neutral and coast. At this point, killing the engine is optional (but a very dangerous option).
      1. Downhill?
      2. Trailer truck/bus up ahead? Always remember to observe safe following distances!!!
      3. Running fast enough (around 50 mph [80 kph])?
   4. If you killed the engine, you will need to pushstart it:
      1. Shift the gear to match the speed push the clutch down.
         10-19 kph (6-11 mph) - 1st gear
         20-39 kph (12-24 mph) - 2nd gear
         40-59 kph (25-36 mph) - 3rd gear
         60-79 kph (37-49 mph) - 4th gear
         80 kph (50 mph) - onwards - 5th gear
      2. Quickly release clutch and step on gas until motor starts.
   5. If you kept the engine on, match the speed to the gear and shift into the correct gear:
      10-19 kph (6-11 mph) - 1st gear
      20-39 kph (12-24 mph) - 2nd gear
      40-59 kph (25-36 mph) - 3rd gear
      60-79 kph (37-49 mph) - 4th gear
      80 kph (50 mph) - onwards - 5th gear

Disadvantages of FAS
FAS is great for manual transmission vehicles, but you need to match the speed to your gear when resuming acceleration after an auto stop. Not doing so will shorten the lifespan of your transmission gears and clutch gears (slow engine + fast transmission gears = detonated clutch). Failure to match speed to gear will result in locking up your wheels. Thus, you lose control in those few moments - not something you want happening on a slippery highway.

If you turn off the engine during a FAS, there is also the off-chance that the car wil not restart (mechanical/electrical issues not enough momentum to pushstart again, etc.)

Another con is that automatic transmission cars will experience transmission and clutch degredation shortening the lifespan of these said parts. Cars with CVT (continuously variale transmission) would not act favorably to the engage-release cycle that you do as well.

Advantage of FAS
Fuel economy (as per my experience, I recorded an average 10% savings)

How to FAS using a hybrid vehicle
Set the autostop setting (consult your car manual).
Drive to meet the FAS conditions, then let go of the accelerator.