^The Injectors in my Swift turn on at 1400 RPM. I always coast and Rev match when Down-shifting 
Now, I'll explain it in simple words;
Scenario A;
[I]You are driving at 90km/h. You put car in neutral, RPM will drop to Idle and fuel will be consumed to keep Idle RPM. Why is that? The Wheels are still turning, how can that happen? Simply- Because the Clutch plates are not engaged, hence not turning the engine. This is why you have less control over the car.
[/I]Scenario B;
[I]You are driving at 90km/h. You release Accelerator in 5th gear, In most ECU controlled cars, the Injectors will turn off- There is no need for fuel to be consumed, since the Wheels are turning the engine and powering your AC Compressor and Alternator etc.
When RPM drops down to 1200-1400, you will feel a tiny jerk ( Usually, most easier to notice at low speeds- Under 40 km/h.) That's your cars Injectors turning on and spraying fuel to avoid the engine stalling.
[/I]
What I do- Let RPM come down to 1400, Engage the clutch, Rev to 2000 RPM, put car in 3rd gear and release the clutch. RPM will jump up to 2050 RPM, hence, keeping my Injectors off, getting infinite Fuel Average.
So- Car in Neutral while moving = Idle RPM = Fuel used
Car in Gear over 1400+ RPM = Injectors turned off = No Fuel used.
Btw- The downshifting in Scenario B, you have to do it quickly, otherwise you will experience a tiny bit of wear and tear on your Clutch Plates.
Any questions, feel free to ask 
