That may be true but while costing in gear, the fuel that it is still burning is no more than what it would be burning while the engine is idling while the transmission is coasting in neutral. So to be popping it into neutral to save fuel isnt going to help or be noticeable either way.

The only difference I can see would be how far the car could coast in neutral versus being engine braked and then gas added to maintain speed.

For example if the goal was 25 mph and you were doing 50 mph then you could take longer to get to 25 mph by placing the car in neutral. If you left it in drive it would coast down faster to 25 mph and then you would have to add gas a little earlier to maintain 25 mph.

So while it may save a little gas, to me it has disadvantages as well that for nearly everyone offsets any possible benefits.

I think most hypermilers would state that the most important factor is maintaining average speed for the conditions. For example instead of stop and go in a traffic jam you maintain the average speed that the traffic actually moves forward so you are neither accelerating or braking (unlike how most of us do it). Not only do you save fuel but so does everyone around you.

The link didn't seem to want to work but in any case computers predated the automobile.

Until you get to a certain point there is no fuel going to the motor. Now, I do not know what point that is but I do know there is NO fuel. I said in my previous post I have an air/fuel gauge and it tells me how much fuel there is to air. When there is no fuel going through and just air, it reads "---". When coasting it reads "---" therefore no fuel is going in the motor.

pfarmer, you mentioned in your post about stop and go traffic. I am not referring to stop and go traffic, I am referring to coming off of high speeds where the revs are at least 2,500. Of course you are going to burn fuel sitting in traffic and stopping and going. But coasting from high way speeds will save fuel. I believe Jeremy from Top Gear even stated in an episode that the modern engine burns no fuel when coasting.

I had a 94 Ford Taurus SHO that used to pi$$ through brakes two to three times a year.
The dealer told me that the only way to slow down this rediculous brake wear was to pop the car into nuetral whenever I was braking.
I thought this was a pretty lame solution but they claim that even at an idle, the engine pushed the car much more than when in nuetral, and this in turn would help to save my brakes.
I never did it... too much of a hassle and I ended up getting rid of the car about a year later. Damn thing passed everything but a repair station.

I may be naive, but can someone explain how the engine will stay on with no fuel in it? Isn't the engine always spinning at 600-2k rpms when coasting, therefore spark plugs are firing, and it's moving? or do the wheels move the engine? I'm just confused.

If the engine is running, it's consuming fuel.
I think what they're trying to say is that in a modern engine, at idol, it uses almost no fuel.

the first electronic computer was made in the 40s

you know exactly what i meant. Computer controlled automatic transmissions did not come around until the last few decades.

You said what I want to say.

Of course, coasting on high way in N is not a good thing to do. But in a situation there is a traffic ahead, it is better to shift it into N and let the car goes by itself until you need to stop or give it some gas to speed up (the gear is putting back to D).

I didn't state it was better, only that maybe it would say a very small amount of fuel by doing so.

Jeremy may have stated that and he may well be incorrect for the Infiniti. As far as your a/f gauge telling you that the engine is not burning fuel during a coast mine can be set up to tell you the same thing. It is a setup issue in its case. Basically some cars will report that the injectors are cut off at a certain throttle position, often a couple of percent above 0. The cutoff value is typically checked against the status of the close/open loop of the fuel system which indicates if the oxygen sensors are used to control air fuel mixture.

If your gauge sees what it thinks is no fuel with a closed loop it will most likely error out on an a/f gauge since it can not divide by zero. Simply displaying ---- doesn't mean the engine is not burning fuel, it means the gauge can't compute the value with the parameters present.

Even if it wasn't burning fuel during a coast versus putting in neutral, neutral would probably still win in the gas use race since the minimum amount of fuel burned is less than what is now being wasted by engine braking. The difference being how far can you coast from lets say 60 to 50 using engine braking versus neutral with no engine braking. Still doesn't mean it is a good idea.

Actually the first 'commercial' electronic computer was made in the 40s. There were earlier electronic examples and many mechanical ones prior to this. In fact the first digital was probably about 1642. The point is that in reality even some of the early automatics can be said to be controlled by what we commonly refer to as sensors. Throttle position may have been mechanically derived in most cases but some cars did use electronic switches to control certain things as well. While the governor in most early Chrysler autos may have been hydraulic internally the governor that controlled the highest gear in my 53 Plymouth was electric and engaged at 28 mph (when it worked). Of course in this car the highest gear was the only totally automatic one. The governor was in series with a switch located near the carburator. This is where I attached my bypass so it would engage at any speed and could also be disabled at any speed.

So while I know that you meant totally computer control auto, various elements existed much earlier. Still not really a good idea to shift into neutral to save two drops of petro. In some cases even power steering will not function the same at idle as it does at normal rpms at a given speed. If the car stalls other issues come into play as well.

I tap my + paddle quite often during long downhills or if I am decelerating onto my driveway or stop sign. This holds 5th longer than leaving it alone, so in downhills where you would be in 5th anyway it does not gain anything. I feel a noticeable reduction in engine drag at speeds around 30-45MPH. Not sure if it really saves anything. It might be an alternative to going N.

Everytime you tap the gas you are using a little extra fuel. If your intent is to hold it in 5th, why not just put it in 5th.

I am putting it in 5th, that's what the + paddle does. Since I am decelerating or trying to coast I am not hitting the gas , I think you misunderstood.