On many cars you may notice that the gear shifter has two Ds. You know what park, reverse, & neutral are. You hopefully also know that the numbers are for explicit downshifting, but why does drive appear twice?
The first D with a white background is really meant to be a D inside of an O for "overdrive." This enables all of the gears in your transmission and allows you to go into the highest gear, which is sometimes called "overdrive," to optimize your MPG on the highway. The lower, pl...