Well happy to answer your query- The more time you keep you car at Idle, the FE will drastically go down.
Running in neutral is not called idling,
and this should be avoided too.(will come back to it)
Idling means your car is stationery and engine is running.
The details-
HERE'S THE RULE OF THUMB: If you're in a drive-through restaurant, long ques at fuel station, Traffic signal with timer,or waiting for someone and you'll be idling and sitting for 10 seconds or longer... turn off your car's engine. Why??
For every two minutes a car is idling, it uses about the same amount of fuel it takes to go about 1.5 km. Research indicates that the average person idles their car five to 10 minutes a day.
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