Mexican overdrive

Etymology
Based on NASCAR teams' experience in the early 1950s in the legendary Carerra Panamerica, where the long hills would have otherwise overrevved the engines.

Noun

 * 1)  The neutral gear when used while a vehicle is moving, especially when it is used to save fuel or to coast downhill faster than a vehicle can go in gear. (This is illegal in some places.)
 * He shifted his car out of gear, at the top of the hill, and coasted down in Mexican overdrive.