(I got the idea to try this after reading some articles on "Hyper-Mile" driving... I do not recommend doing this for safety reasons)
I've conducted 2 experiments with my 2000 Honda Accord 4cyl, and both experiments were quite impressive....
The baseline MPG i currently get on my 2000 Honda Accord with regular, in-city driving is 21.5 mpg...
I've tried experiments with acetone and HHO, but my experiment with neutral breaking and idling is currently my biggest success....
I average 30 miles a day in-city driving... with a great deal of start-stop driving with traffic lights (about 15 traffic lights on my daily route). I decided, for my experiment, to completely run my tank from full to nearly empty at least twice while using neutral at every opportunity while driving (whenever I break/coast coming toward a traffic stop, or while at a complete stop at a traffic light).
For the past two tank fulls, I've been able to calculate (divide the number of miles traveled by the amount of gallons of fuel needed to "top-off" my tank after running it to nearly empty), and in both instances I've had a net gain of +2 MPG while doing this...
Here are my statistics:
My current average fill-up with normal driving is:
320 miles on 14.875 gallons - approx 21.51 mpg
My 2 experimental fill-up's have provided the following results:
327 miles on 13.900 gallons - approx 23.53 mpg
317 miles on 13.500 gallons - approx 23.48 mpg
current average between my first two results: 23.505 mpg.... a net gain of 1.995 mpg
I'm going to conduct a few more experiments..... and research the neutral shifting capabilities of my 2000 Honda Accord to see if it is mechanically or electronically controlled.... If it's electronically controlled I hope to successfully find a way to tie in breaking to automatically shifting into neutral... helping me be even more consistant with doing this each time....
Again, manually shifting to neutral while rolling or at a stop may be dangerous to drivers who are not use to doing this and are forgetful .... and could possibly lead to an automotive accident if a quick response to changing driving conditions occurs (i.e. - needing to apply gas quickly to avoid an accident, but forgetting you still have the car in neutral)...
please attempt this at your own risk.
PwrDream