Freewheeling is not dangerous for small cars..but big trucks quickly loose the breaks (break drums heat up at high speeds and expand...then linings can't reach them,therefore no breaks....I used to be a truck driver some 25 years ago!!). Small cars have discs and pads at leats on front wheels therefore they don't experience that problem....and the are not heavy,therefore they won't generate much heat even at very high speeds.
However; never,ever,turn off the engine when free-wheeling. If you do,you will definitely loose the breaks and you might also lock the steering!!!
The amount of fuel you save might be insignificant,therefore not worth the bother!
Putting to neutral in a jam also DOES NOT save much fuel. If you want to save,turn off the engine when you are in a jam.....and when the traffic moves,lock the automatic in top gear (in some cars,the button for locking is labeled 'over-drive'; in that case,disengage the overdrive and put the car in top gear)
You know you are locked-in if the acceleration is slugish and the car doesn't change gears.
Anothe method of saving fuel with an automatic is to speed-up the gear changing sequence. You do this by letting go the accelerator pedal momentarily and pressing down again. This forces an 'early' shift to the next higher gear.
But if you think this is too much work; then just drive gently (and by 'gently',I don' necessarily mean slowly!!!!).
Driving style is the greatest contributor to excessive fuel consumption. The guy who picked my car from the port consumed a tank and a quarter driving it to Nairobi! When I do the same journey in the same car,I consume slightly under three-quarters of a tank!
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