Selective catalytic reduction, or the urea system, uses the ammonia-based acid to reduce NOx emissions from diesel engines. Unfortunately, the system requires car owners to periodically refill the on-board urea tanks. The EPA will decide, in the following weeks, what methods to ensure drivers keep those tanks filled. Areas of discussion include from warning system to locking fuel caps (until the urea tank is filled) to fully disabling the vehicle. Automakers, who will have to develop the system, especially oppose the latter, warning of safety issues.
Our take? This is a tricky one. As much as we like diesel, we don’t like our cars stalling because we forgot or were too busy to refill the urea tank. The analogy comparing urea refills to oil changes falls flat because diesel cars can run perfectly fine without the system. (Try that without changing your oil.) Maybe having an extra hose at the gas station will eventually get motorists into the habit of refilling the tank.