A drive belt is a loop of flexible material used to link two or more rotating shafts mechanically, most often parallel). It is an essential part of a vehicles engine bay, responsible for running multiple components such as the air conditioning compressor, power steering, radiator fan, water pump, and more. There are three types of drive belts: serpentine belt, V-belt, and timing belt. The serpentine belt is located under the hood of a car and snakes its way between various pulleys and accessories. It is usually found in cars produced after 1990 and tends to last longer than other types of drive belts. The V-belt runs off a crank and pulley and typically travels between one or two engine accessories. Older cars often have several V-belts used for power steering, air conditioning, and other operating essentials. V-belts can be more difficult to change than serpentine belts. The timing belt is responsible for synchronizing the engines camshaft and crankshaft rotation. It is often beneficial to change the drive belts in a car approximately every 60,000 to 100,000 miles. If any signs of damage or severe wear and tear are identified, the belts should be replaced. Drive belts are simple, inexpensive, and do not require axially aligned shafts. They help protect machinery from overload and jam, and damp and isolate noise and vibration. Load fluctuations are shock-absorbed (cushioned). They need no lubrication and minimal maintenance. They have high efficiency (90–98%, usually 95%), high tolerance for misalignment, and are of relatively low cost if the shafts are far apart).