Why is my car giving off a sulfur odor?

WHEN: All the time, especially after the vehicle has been sitting after a long drive.

THE CULPRIT: Yes, it really is brimstone, or, as it is usually called today, sulfur. This means gear lube is leaking from the manual transmission, transfer case or differential housing. Sulfur compounds in this oil serve as extreme-pressure lubricants for the gears, and can get pretty funky after a few years in service. Look for sulfury-smelling dribbles of viscous, oily stuff under the car. Unfortunately, leaks here typically mean a trip to the shop