Internal combustion engines are very inefficient. Due to the rising cost of oil due to different influences (OPEC, War, terrorism, "limited supplies" (sure...), etc) the market for alternative fuels is opening at an incredible pace, and the pursuit for an alternative (read: cheaper) option such as hydrogen is sucking billions of dollars from the major manufacturers in development. Petrol will be superseded by about 2012, by probably hydrogen. Petrol will still be available; it will just be too expensive to be viable as a primary source for transport. The price of petrol will plateau, probably at about $5-$6/litre, and will become secluded to the comparitively small consumer group of enthusiasts (a few people here included) who drive petrol-powered cars as recreation, rather than transport. The larger manufacturers will continue to produce petrol-powered sportscars until about 2017, where the market dies off due to its declining sales. The exotic manufacturers will continue to make petrol-powered supercars, until petrol is ultimately put under pressure to be phased-out around 2025 (due to its environmental 'impact', albeit small at this point) where petrol will then become a specialty product, much like racing fuel is today (purchased in drums and stuff). It will be used only by the most dedicated enthusiasts, for decades on, but it will never "run out".