An exhaust gas recirculation (EGR) valve is responsible for recirculating a small amount of exhaust into the combustion chamber.

Although the carburetor was an important part of the vehicle decades ago, the fact is that almost all modern cars made in the past 20 years do not have one, instead opting for fuel injection systems.

Fuel efficiency can be a difficult metric to track, as the difference between 38 miles per gallon and 40 miles per gallon isn't exactly obvious to most drivers.

Automobiles are complex machines, and it's nearly impossible for a driver to understand every aspect of their vehicle.

Prior to 1990, car engines were still built with carburetors as the means of supplying fuel to the combustion chamber, but after that all vehicles were instead equipped with fuel injection systems that are able to provide a more precise amount of fuel.