To save gasoline by putting a car into neutral (or depressing the clutch) when going down a hill.

The origin is uncertain, since Okies are not likely to encounter sizable hills on their native turf.

Compare with Jewish overdrive.
Janey Ellen put her Chevy pickup truck into Okie overdrive to go down Coon Holler Hill.
by Cap'n Bullmoose April 21, 2005
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