straight chain paraffins

aromatics

branched chain paraffins

napthalenes

brake power

compression ratio

specific air consumption

mean effective pressure

engine can run

engine gives maximum output

engine is most efficient

fuel can be used in a test engine without knocking

tool lean mixture

stoichiometric mixture

most economical mixture

too rich mixture

spark plug gap too small

spark plug gap too wide

vapour lock in the fuel only

incorrect fuel air mixture