The fuel line system found in modern cars can get pretty complex. Luckily, the most complex ways vehicles save fuel involve programming in the ECU. Physically, there are only a handful of fuel system layouts to be found under the hoods of modern cars.

A car’s gas tank is responsible for holding the vast majority of the gas in the fuel system. This tank can be filled from the outside via a small hole that is sealed with a gas cap when not in use. The gas then goes through a few steps before it reaches the engine.

Rather than letting the engine draw in gas via its own pressure alone, electronic fuel injection uses a fuel pressure regulator to keep a steady vacuum of pressure drawing fuel to fuel injectors that spray a mist of gas into the combustion chambers. There are single-point fuel injection systems that introduce gasoline into a throttle body mixed with air. This air/fuel mixture then enters all of the combustion chambers as needed. Direct fuel injection systems (also called port fuel injection) have injectors delivering fuel right into the individual combustion chambers and have at least one injector per cylinder.