Sour Diesel displays an extremely pungent blend of fuel, skunk, citrus, and spice that will leak through many jars and bags when the strain is well-grown.  The sharpness gets stronger after breaking it up, adding a stronger kick of citrus as well as a cutting fuel aroma that tickles the nose.
A frontal attack of skunky citrus funk gives way to a mentholated lime-kissed spice which lingers in the mouth.  The smoke is expansive and will definitely cause coughing on larger hits.
Sour Diesel is fairly Sativa-dominant but seems to exhibit a headslam of an Indica effect at times, especially if let go late into flowering.  It hits the eyes and head immediately, filling them with pressure and energy, while the body seems almost immobile at times, trending heavily towards couchlock — a numbing quality is also often reported, aiding with nerve and muscle pain relief.