Simply put, D means drive, and D3 means Drive-3. When you put your car in D3, that means you've set third gear as your highest setting, whereas you can reach every gear of your car in D.

Ever wondered what the "1" and "2" on your automatic gear shift mean? Learn how these low gears work and when you should use them.

On the surface, there’s no way the climate control or headlights could affect the way a transmission works, but here we are… The most likely explanation is that the electrical gear that’s locking the ...