Letting a vehicle idle does more damage to the engine than starting and stopping. In fact, running an engine at low speed (idling) causes twice the wear on internal parts compared to driving at regular speeds. “Excessive idling has a negative effect on the engine and exhaust system and increases maintenance costs.” “For instance, extended idle operation may lead to reduced efficiency of engine lubricants (increase in frequency of oil change), engine or spark plug wear/fouling and accumulation of fuel residue in the exhaust system”.