[kgwedi]

I decided to do some testing to find a numerical value for the fuel savings between Engine Off Coasting (eOFFc), and Engine On Coasting (eONc).

On my normal routes, my Metro gets close to 58 MPG. I drive slow, and have the advantage of good breakdown lanes that I drive in. Traffic is seldom a factor on this route. My normal commute is 66.4 miles round trip. I maximize the use of "pulse and glide" ( "accelerate and coast" ).

Of the eco mods done to my Metro, the button on the gearshift that opens the power circuit to the fuel injector is my best eco mod. I accelerate to an optimum speed (depending on terrain) then push in the clutch, push the button on the gearshift until the engine stops. If it will be a long coast, I'll put it in neutral, otherwise just use the clutch. To restart I just pop the clutch (usually in 5th gear).

I decided to use timers ( like a chess timer) to see how long my engine ran, versus how long it was off. One leg of my trip is 33.2 miles. This section is basically level, with a slight tail wind, and about a 150ft decrease in altitude.

The 33.2 miles took 46 min 32 sec. That is an average speed of 42.8 MPH. I try to accelerate to about 55mph and then coast to about 35mph. This varies with terrain. Total fuel burn was .56 GAL.

During this 46 minutes, my engine was off for 1256 sec (20min 56sec) and on for 1535 (25min 35sec).
At idle my Metro burns .13 GPH.

1256 seconds is .349 hours. So I saved .13 GPH for .349 HRS. Which is equivalent to .04537 GAL.
Since total fuel burned was .56 gal, the fuel saved was 8.1%
If I had used eONc then I would have burned .605 GAL in total.
I didn't know if I should have used percent of fuel NOT burned (i.e.. saved) or percent of total fuel used, that could have been saved..( I got confused ) :-)

Here is a quick algorithm check:
An average of 60 MPH, for 1 Hour, using 1Gal of gas.
That is an average of 60 MPG. Engine off 50% of the time.
Fuel saved = .13 GPH for .5 HR = .065 GAL.
That's a 6.5% fuel savings. So my figures are in the ballpark.

A long uphill or a long downhill would drastically change the percentages. For my own use, I'll plan on between 6 and 10% MPG improvement using eOFFc versus eONc.
The lower the total drag, the longer the coast. Better aerodynamics, and lower rolling resistance will increase the benefits gained by eOFFc versus eONc.

I can expect a fuel savings of about .1 gal a day if I use eOFFc instead of eONc. That is about 35c a day in gas savings. Or $7.00 a month.