Gasoline also known as petrol outside North America, is a transparent, petroleum-derived liquid that is used primarily as a fuel in internal combustion engines.It consists mostly of organic compounds obtained by the fractional distillation of petroleum, enhanced with a variety of additives. On average, a 42-gallon barrel of crude oil (159 L) yields about 19 US gallons (72 L) of gasoline when processed in an oil refinery, though this can and does vary based on the crude oil source's assay. The characteristic of a particular gasoline blend to resist igniting too early (which causes knocking and reduces efficiency in reciprocating engines) is measured by its octane rating.
Gasoline is produced in several grades of octane rating.
Tetraethyllead and other lead compounds are no longer used in most areas to regulate and increase octane-rating, but many other additives are put into gasoline to improve its chemical stability, control corrosiveness and provide fuel system 'cleaning,' and determine performance characteristics under intended use.
Sometimes, gasoline also contains ethanol as an alternative fuel, for economic or environmental reasons.Źródło: https://en.wikipedia.org/wiki/Gasoline
Some of them you can fix in just a few hours, but others require special equipment and skills that have only appropriately trained specialists in this field.