<Tr> <Th> </Th> <Th> Primary (natural) </Th> <Th> Secondary (artificial) </Th> </Tr> <Tr> <Th> Solid fuels </Th> <Td> wood, coal, peat, dung, etc . </Td> <Td> coke, charcoal </Td> </Tr> <Tr> <Th> Liquid fuels </Th> <Td> petroleum </Td> <Td> diesel, gasoline, kerosene, LPG, coal tar, naphtha, ethanol </Td> </Tr> <Tr> <Th> Gaseous fuels </Th> <Td> natural gas </Td> <Td> hydrogen, propane, methane, coal gas, water gas, blast furnace gas, coke oven gas, CNG </Td> </Tr>

Small steps of fuel conservation can make a big change in 700 words wikipedia