Can Somebody Explain Hypermiling To Me?

Hypermiling consists of maximizing your miles per gallon. By changing your driving habits, you might be able to get somewhere around 30% better mileage.
Some take it to the extreme and do things such as turning their car off while it’s rolling. Dangerous and doesn’t actually do much.
Accelerate slowly, avoid braking as much as possible (start slowing down earlier), and try to minimize the distances you travel. These will yield the best results.

Just that act of doing all sorts of things to get better mpg. From turning a car off going down hill to driving where you make more right turns so you have to stop less and all sorts of other odd stuff.
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Driving to achieve the best mileage possible.