Nice figure, I'd still like tom know how much the MPG will change if not using the feature vs using at the time. I guess on one of our trips (after we get the damn thing), we use it going one way, and not coming home. Now this won't be totally fair seeing we will be driving downhill going south when in use and going uphill driving back north
Maine to Quantico likely to be the first big trip
I drove my Mirage down my test track (deserted road) and got over 150 MPG with engine off coasting, about 3.3 miles in 6 minutes 20 seconds. Same test drive with the engine idling the MPG dropped 50%. So the same amount of fuel used uselessly running the engine, used to provide propulsion contributing nothing to vehicle movement was used as the amount used to move the vehicle at 28 MPH average speed using the power of the vehicles inertia to cover 11/12ths of the distance travelled.
Its been around over 2 decades, I owned a 2000 Honda Insight with start stop. The engine idled at 150 MPG with the vehicle coasting in neutral (CVT transmission) at 15 MPH using about .11 GPH. My neighbors V8 Chevy used .5 GPH idling. My Insight would go 40 MPH on that same .5 GPH consumption.
Obviously if you are on cruise control at highway speeds, then there would be NO savings. The savings is huge when you are crawling at almost gridlock conditions, especially with the hybrid battery providing all of the propulsion for a decent amount of distance and you use no liquid fuel, so the savings is 100 %.
Your average is totally dependent on you average driving environment somewhere between those two extremes. Trips help only where you encounter stop and go driving. Local multi stop commutes are where start- stop shines.
Your test conditions given the choice of driving environment will show it to be a total waste Try a commute to work and back with numerous traffic lights.