If P&G does not give better results you are doing it wrong and reasons are many:
- too much speed for cars Cd as it was in this case
- Trying to do it in a "big" uphill. Or even smaller depending on the case
- cars weight
- Cars rolling resistance
- You leave the car to gear
- not best gas position on accelerations
- Power to weight ratio
Yesterday I was educating fuel saving driving techniques in a truck thats total weight was 45 tonn. P&G did work in downhills. downhill was 1 meter down in every 70 meter distance and we already rolled
. speed did slow down much in that small hill, but it worked. If it was level or even little uphill it did not work.
On next day we had 50 tonn and it did not work anymore pushes were too long at 80 to 88 km/h speed. We would have need to slow down to see the positive results. However we were still able to coast in neutral on deeper hills.
Also I noticed that your eye lies about 50% of the time in small hills is it downhill or uphill. Only way to tell was to watch height from navigator,
very helpful tool in that job! On a bigger heavier and worse aero car or truck it will work on downhills. With better power to weigth ratio car and if aero is good you can do it almost everywhere and see better results.