There are a number of benefits to filling tractor and large truck tires with nitrogen instead of air. Although pumped air is 78 percent nitrogen, the rest is mostly oxygen, which causes moisture in a tire. Moisture in a tire can cause a tire to deflate faster, rubber compounds to break down and metal tire parts to corrode.
Fuel economy is always helped by consistent and accurate tire pressure. Nitrogen-filled tires have more consistent pressure, according to "Consumer Reports." Many large truck fleets use nitrogen in their tires to maintain the correct tire pressure longer, to slow the aging of the rubber and to prevent overheating and promote optimum tread life. According to a U.S. government website on fuel economy, tires that are properly inflated improve fuel economy by up to 3 percent.
Several factors play a part in the longevity of a tire. Tire pressure, the durability and strength of the rubber and tire heat all contribute to a tire's life. When moisture is removed from the inside of a tire, its durability and strength are not compromised. Heat can reduce the life of a tire dramatically; nitrogen-filled tires remain cooler.
Tires filled with nitrogen are safer than tires filled with compressed air for a number of reasons. Nitrogen does not support combustion, according to the Tire Retread Information Bureau. Nitrogen-filled tires also retain their shape longer because there is no moisture permeating the rubber and causing breakdown of the rubber compounds.
According to the Tire Retread Information Bureau, the use of nitrogen in tires promotes stronger casings that are more easily retread. It takes 22 gallons of oil to produce one new truck or bus tire, 7 gallons of oil to retread a tire. Tires that are retread preserve oil supplies and fewer rubber trees are tapped.
According to the Straight Dope, a free weekly column dedicated to fighting ignorance by answering unusual questions from readers, filling up automobile tires with nitrogen does not make much sense because it is too expensive. Compressed air is 78 percent nitrogen, 21 percent oxygen and 1 percent other gases. Straight nitrogen won't hurt car tires, but it is not necessary.