Propane is a clean fuel, which offers a range of properties closest to that of petrol. It is a by-product of petroleum refining natural gas production. Propane, under moderate pressure turns to a liquid form and is stored in fuel tanks at approximately 6-bar, although propane fuel tanks will withstand 32-bar. When drawn from the tank, liquid propane changes back to a gas before it is burnt in the engine. Propane powered vehicles offer many advantages, not least of which is the overhaul reduction in engine wear. Ignited propane has clean burning properties and is unique as it contains no lead or carbon deposits that degrade components such as valves, spark plugs, pistons and rings. This results in overall reduction of maintenance costs.